Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session CTP: Poster Session I (11:00-12:30) |
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Room: 8 and 251 |
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CTP.00001: INDUCTIVELY COUPLED PLASMAS |
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CTP.00002: Fluid/MC simulation of mode transition in argon inductive discharge with the adjustment of impedance network Shu-Xia Zhao, Fei Gao, You-Nian Wang A complete external circuit has been added into the hybrid Fluid/MC model to investigate the effects of the matched condition of the whole impedance network on mode transition in argon inductively coupled plasma. This circuit composes of the invariable voltage radio-frequency (rf) source, the $\Gamma $-type matched impedance network, the coil and the inductive and capacitive plasma-transferred impedances. In the simulation, the coil current and voltage drop across the coil, as well as the phase between them, are self-consistently calculated from the circuit. When the series capacitance is monotonically increased, the discharge first transfers to H mode and then drops to E mode again, gradually. During the process, the plasma density at the axis center first increases and then decreases, and meanwhile the electron temperature here displays the opposite trend. In addition, the profiles of temperature during E mode are rather smooth, and they peak obviously near the coil in H mode. The mode transition is presumably triggered by the power variation arising from the change of the matched condition of the circuit. The real part of the complex coil current and the imaginary part of the coil voltage both approach to their maxima when the discharge circuit is located in pure-resistance case, and away from this point they reduce significantly. The dependence of the circuit property on the inclusion of plasma impedance is also discussed. The evolution of the whole circuit resistance is strikingly influenced after the plasma transferred impedance is included. [Preview Abstract] |
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CTP.00003: Laser Initiated, RF Sustained Air Plasmas John Scharer, Jason Hummelt, Ryan Giar Measurements and analysis of air breakdown processes and plasma production by focusing 193 nm, 260 mJ, 10 MW high power laser radiation inside a 6 cm diameter helical RF coil. We observe quantum resonant multi-photon (REMPI)$^{1}$ and collisional cascade laser ionization processes in nitrogen, oxygen and air that produce high density (ne$\sim $7 x 10$^{16}$-10$^{18}$/cc) cylindrical seed plasmas at 760 Torr. The focused laser and associated shock wave produces a seed plasma that exhibits REMPI processes for oxygen in the air mixture that enhance the breakdown and ionization process. Observation of nitrogen emission spectra provide density and temperature information for the laser formed plasma. The objective is to provide rapid air breakdown with sustainment at lower RF power levels than required for RF breakdown alone. Measurements of the helical RF antenna plasma load impedance obtained by measuring the reflection coefficient and 105 mm wave interferometer density and temperature measurements are made. Spectroscopic measurements of the plasma and comparison with the SPECAIR code are made to determine rotational and vibrational temperatures. Comparison of the experimental measurements of helical antenna plasma loading with the ANTENAII code will be made and discussed. [Preview Abstract] |
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CTP.00004: Properties of inductively coupled rf CH$_4$/H$_2$ discharges Takashi Kimura, Hiroki Kasugai Experiments with a Langmuir probe and optical emission spectroscopy combined with actinometry are carried out in inductive CH$_4$/H$_2$ plasmas in the total pressure ranges from 25m to 100mTorr. These plasmas are produced in the cylindrical stainless steel chamber with 160 mm in inner diameter and 75 mm in length, where the power injected into the plasma is 140W. The measured electron energy probability functions (EEPFs) are approximately Maxwellian. The measured electron density, which is on the order of 10$^{16}$ m$^{-3}$, gradually decreases with increasing the hydrogen fraction, whereas the measured effective electron temperature gradually increases. The density of hydrogen atoms estimated by actinometry gradually increases with the increase in hydrogen fraction, whereas the intensity emitted from the excited molecular hydrogens is detected even at pure CH$_4$ discharges, and then gradually increases with the increase in the hydrogen fraction. The relative CH and C$_2$ densities, which are roughly estimated from dividing the intensities emitted from the excited CH and C$_2$ by the electron density, decrease with the increase in hydrogen fraction. A global model for electropositive plasma is used in order to investigate the plasma chemistry in CH$_4$/H$_2$ discharges assuming the Maxwellian electron energy distribution. The model results are compared with the experimental results, obtaining reasonably good agreement. [Preview Abstract] |
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CTP.00005: EEDF and Plasma Parameters of ICP in Dipole Magnetic Trap Valery Godyak Electrical and plasma parameters were measured in an ICP excited with an immersed cylindrical antenna coil having a permanent magnet at its axis. The magnetic field structure formed a dipole magnetic trap leading to a strong stratification of the ICP into two zones. One, the hot plasma zone, that was localized near the antenna and consisting of dense plasma with large electron temperature (comparing to those in the same ICP without magnetic field). The other, cold plasma zone surrounding the first one, consisted of cold electron having there temperature much smaller than without magnetic field. The temperature reduction in this zone was result of magnetic filer effect leading to trapping of high energy electrons within the hot zone. Found a strong spatial non-uniformity in the EEDF and in plasma macro parameters was explained with magnetic filter effect at the condition of braking of electron kinetics non-locality in the presence of magnetic field. [Preview Abstract] |
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CTP.00006: Dynamics of unstable Ar/Cl$_{2}$ inductive discharges Emilie Despiau-Pujo, Pascal Chabert, Allan J. Lichtenberg Instabilities have been observed in inductively coupled Ar/Cl$_{2}$ discharges near the transition between capacitive (E) and inductive (H) modes [1]. A global model, based on five particle balance equations and one electron energy balance equation, was previously proposed to describe the instability mechanism in pure chlorine [2]. The consideration of multiple ions and dissociated neutral species showed that gas chemistry had a significant influence on the unstable cycle but the quantitative predictions of the model could not be compared to measurements. In this paper, argon is added to the model. The influence of argon dilution on the instability process is investigated and simulations and experiments are compared. When adding chlorine to the mixture, the unstable window broadens in absorbed power but narrows in pressure. The frequency of oscillations increases both with pressure and chlorine content. Although some quantitative differences remain, numerical predictions of instability frequency and charged particles densities are in reasonable agreement with experimental data.\\[4pt] [1] CS Corr et al, App. Phys. Lett. 86, 141503 (2005)\\[0pt] [2] E Despiau-Pujo et al, Plasma Sources Sci. Technol. 18, 045028 (2009) [Preview Abstract] |
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CTP.00007: E-H heating mode transition in high-pressure helium inductively coupled plasma Hyo-Chang Lee, Jung-Kyu Lee, Chin-Wook Chung Inductively coupled plasma (ICP) are known to have two distinct modes, capacitive mode (E mode) at a low plasma density and inductive mode (H mode) at a high plasma density, and the heating mode transition from E mode to H mode occurs with abrupt increase in the plasma density at a high gas pressure. However, a smooth transition of the plasma density on the E H heating mode transition was observed in high-pressure helium discharge from the measurement of the electron energy distribution function (EEDF). This result was compared and analyzed with the measured plasma parameters and EEDF in high-pressure argon discharge. [Preview Abstract] |
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CTP.00008: Effect of flow rate on the plasma parameters and electron energy distribution in plasma process reactor Hyo-Chang Lee, Aram Kim, Se Youn Moon, Chin-Wook Chung Effect of the flow rate on plasma parameters and electron energy distribution (EEDF) was studied in plasma process reactor. As flow rates increase at a fixed gas pressure of 5 mTorr, noticeable increase in plasma density and decrease in electron temperature were observed with evolution of the EEDF from bi-Maxwellian to Maxwellian distribution. This result is mainly due to the pressure gradient between a discharge region and a pumping port region where the gas pressure measurement occurs. Based on the measurements of gas pressures at two different regions, a considerable difference in the gas pressure between the discharge region and the pumping port region was found. [Preview Abstract] |
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CTP.00009: Instabilities in an Inductive Coupled Plasma Source With Magnetic Confinement Jaime Arancibia Monreal, Pascal Chabert, Valery Godyak An ICP excitation with internal antenna and a magnetic confinement with a single permanent magnet has been characterized. The plasma is produced by an internal coil powered by a radiofrequency generator around 6 MHz[1]. Experiments have been carried out for RF powers up to 100 watts and in the pressure range 1-100 mTorr. Instability regimes were identified for certain values of the parameters: pressure range of 1 to 50 mTorr and power range of 20-100 Watts. These regimes were investigated by measuring the fluctuations of floating potential using a Langmuir probe. The study was done with and without permanent magnetic field. Three regimes were found: (i) Stable regime (ii) Quasi sinusoidal variations of floating potential (iii) Chaotic regime. The formation of plasmoids, which have an azimuthal drift around the coil, seem to explain the sinusoidal variation of floating potential. The chaotic regime has not yet been explained. The phenomenon also exhibits hysteresis behaviour.\\[4pt] [1] V. A. Godyak, 63rd Gaseous Electronics Conference, Paris, October 4-8, 2010. [Preview Abstract] |
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CTP.00010: Energy Flux onto a Substrate during ICP Assisted Sputter-Deposition Yoshinobu Matsuda, Hiroaki Kitagawa, Kenji Mine, Masanori Shinohara Energy flux onto a substrate has been measured with different thermal probes (TPs) by many researchers in the RF plasma, RF magnetron plasma, and DC glow discharge plasma in the past. However, no measurement of the energy flux onto the substrate during the ICP assisted sputtering has been done as far as we know so far. Therefore, we have measured the energy flux onto the substrate during the ICP assisted sputtering by using a temperature equilibrium type TP that operates with a time constant about 100s. The energy flux was proportional to the target power in a pure planar magnetron, and it was proportional to the ICP power in a pure ICP. However, the energy flux in the ICP assisted sputtering is not a simple addition of the energy flux in the pure planar magnetron and that in the pure ICP; i.e., the energy flux in the ICP assisted sputtering is predominantly determined by the ICP power. The energy flux measured with the thermal probe was in good agreement with the calculated results, which were based on the model proposed by Kersten et al. [Preview Abstract] |
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CTP.00011: Measurement of metastable fractions and effect of stepwise ionizations in inductively coupled argon plasmas by optical emission spectroscopy Young-Kwang Lee, Chin-Wook Chung Metastable number densities relative to ground state and contribution of stepwise ionization to total ionization were experimentally investigated in low-pressure inductively coupled argon plasmas. In the pressure range 3--50 mTorr, optical emission spectroscopy (OES) was used to determine metastable fractions by measuring the emission intensities from 4p to 4s levels. The measured metastable fractions were in good agreement with the calculation, showing a dependence on the discharge pressure. The contribution of stepwise ionization was also estimated from the measured metastable fractions along with a model prediction. It is observed that at relatively low discharge pressures ($<$ 10 mTorr) the ionization is mainly provided by the direct ionization, whereas at higher pressure the stepwise ionization is dominant with increasing discharge power. [Preview Abstract] |
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CTP.00012: Electron densities and temperatures in a Cl$_{2}$/Ar ICP Jean-Paul Booth, Rodolphe Sarot, Emilie Despiau, Pascal Chabert, Lina Gatilova, Sophie Bouchoule Electron densities were measured in an industrial inductively-coupled plasma etch chamber in Cl$_{2}$/Ar mixtures as a function of composition (0-100{\%} Cl2), pressure (0.5-10 mTorr) and RF power (100-800W), using both a microwave hairpin resonator (MHR) and a Langmuir probe (LP). The LP results closely tracked the MHR results but were lower by $\approx $20{\%}. In pure Cl$_{2}$ the electron density increased linearly with RF power, and decreased with pressure. The electron temperature (LP) was approximately independent of RF power, and decreased with pressure. The results were compared to fluid simulations based on the HPEM (Hybrid Plasma Equipment Model) code of Mark Kushner. Excellent agreement was obtained for absolute values and trends in electron density and temperature in pure Cl$_{2}$, whereas the density was somewhat underestimated in pure Ar. [Preview Abstract] |
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CTP.00013: Experimental measurement of the plasma parameters in Ar/SF$_{6}$ inductively coupled plasma Seung-Ju Oh, Hyo-Chang Lee, Young-Kwang Lee, Jung-Kyu Lee, Chin-Wook Chung SF6 gas or Ar/SF6 mixing gas is widely used in plasma processes. However, there are a little experimental studies with various external parameters such as gas pressures and mixing ratios. In this work, a study of the plasma parameters were done in Ar/SF$_{6}$ inductively coupled plasma (ICP) from a careful measurement of the electron energy distribution function. At a low gas pressure, as mixing ratio of SF$_{6}$ gas increased at a fixed ICP power, electron density decreased and electron temperature increased, but it was not changed largely. However, a remarkable increase in the electron temperature was observed with decrease in the electron density at higher gas pressures. The variations of electron density and temperature were more dramatic at high gas pressures. These changes in the plasma parameters could be explained by combined effect of large electron losses due to attachment and electron heating. Also, the measured plasma parameters are compared to the theoretical results with simplified global model. [Preview Abstract] |
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CTP.00014: MODELING AND SIMULATION |
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CTP.00015: PIC simulations of low pressure plasmas using graphics processing units Philipp Mertmann, Denis Eremin, Thomas Mussenbrock, Peter Awakowicz GPU-computing (graphics processing units) is a new and fast technology to solve mathematical problems highly parallel. Particle in cell (PIC) simulations can be parallelized for the most part, but still have some modules that can lead to problems when running on a GPU. Programming the code straight forward can actually decrease the speed in comparison with a normal CPU. In this contribution we present different implementations and an outlook on how a two-dimensional code can be approached. [Preview Abstract] |
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CTP.00016: Laser Ablation: Effect on Ambient Pressure on Titanium Plume Expansion Dynamics Farida Hamadi, El-Hachemi Amara In this paper we present a numerical modeling of a nanosecond laser pulse interaction with a titanium target. We investigate the vapor plume formation and the influence of the ambient gas pressure on plume expansion dynamics. The vapor plume formation depends on the results of the heat transfer in the solid target modeling. The solid-liquid phase changing is modeled by a two dimensional approach using an enthalpy formulation. The resulting plume expansion in argon background gas is studied using the species transport model. The algebraic equations are discretized by the finite volume method implemented by Fluent CFD softwares. The calculation results of plume expansion velocity, density, temperature and ionization degrees in the plume are presented. [Preview Abstract] |
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CTP.00017: Kinetic theory approach of the dispersion relation of a cylindrical magnetized plasma waveguide Hadi Zakeri Khatir, Mojtaba Farzin Aghamir The effect of a magnetized plasma column in a cylindrical waveguide is considered on the basis of Vlasof equation. The dispersion relation is obtained through the solutions of the wave equation in the plasma as well as the vacuum regions and the application of the appropriate boundary conditions. The magnetized plasma is considered as collisionless and nondegenerate. The equilibrium particle distribution is assumed to be Maxwellian for nondegenerate plasma. The results of the numerical analyses of this study are compared with the previous investigations in which the MHD equations are utilized for the dispersive characteristics of the waveguide. [Preview Abstract] |
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CTP.00018: Simulation of a PIII reactor with a magnetized remote source Mathieu Maury, Khaled Hassouni, Armelle Michau Plasma Immersion Ion Implantation (PIII) is about to reach the industrial phase, but fine tuning of PIII reactors is still difficult without a correct understanding of the phenomena involved. This is critical in the case of a magnetized cylindrical ICP remote source connected to a large implantation chamber, because plasma coupling mechanisms scale differently in each part of the reactor. A modular simulation has been developed to simulate such a device. First a non-local magnetized electron kinetics model, coupled to a chemical kinetics module treating the relevant reactions for BF3, allows to assess the electron-impact fragmentation of the doping precursor. Then the diffusion of the magnetically expanding plasma from the source to the main chamber is treated with a double layer model. Finally, a Particle In Cell model including all the fragments previously determined is used to determine the sheath dynamics and ion energy distribution on the wafer. The completed model have been fully tested with parametric studies. The plasma chemical composition and ion energy distribution can be readily obtained from the reactor tuning parameters accessible to the operators. The disruption of the source plasma by the implantation pulses and corresponding recovery time have been correlated to the pulse parameters. [Preview Abstract] |
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CTP.00019: Study of reactive hydrocarbon radicals in microwave plasma CVD for synthesis of single crystal diamond Hideaki Yamada, Akiyoshi Chayahara, Yoshiaki Mokuno, Nobuteru Tsubouchi, Shin-ishi Shikata Microwave plasma chemical vapor deposition (MWPCVD) for synthesis of single crystal diamond (SCD), which is operated under quasi-atmospheric pressure, is studied by using numerical simulation. By limiting our interest into the discharge condition which enables to achieve simultaneous improvements of the growth-rate and crystal quality, we simplified the model to prescribe the MWP as much as possible. While the model is simplified, several results seem to be consistent with those given by other models. On the other hand, results of the present model are compared with some experimental results of the SCD growth. Dependences of the species concentrations on the power density and percentage of methane in the feedstock gas mixture are estimated. The calculated results show that the increase of the power density gives simultaneous increases of the absolute concentration of the methyl radical and relative concentration of the atomic hydrogen. The former is considered to be one of the important precursors for the growth, and the later is important for the removal of the non-SCD component during the growth. Therefore, this result is considered to be closely related to mechanism of the simultaneous improvements which have been observed in several experiments. [Preview Abstract] |
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CTP.00020: A model-based analysis of plasma parameters and compositions in HBr mixed with Ar, He or H$_{2}$ Alexander Efremov, Vladimir Svettsov In this work, we carried out the study of steady-state plasma parameters, active particles kinetics and densities in HBr/Ar, HBr/He and HBr/H2 plasmas under the conditions of dc glow discharge (30--120 Pa, 20 mA) excited in a cylindrical (r = 0.9 cm, l = 40 cm) reactor using the 0-dimensional self-consistent model. The set of equations included: 1) The Boltzmann kinetic equation without accounting for both electron-electron collisions and the second-order impacts; 2) The plasma conductivity equation; 3) The balance equations for neutral and charged particles; 4) The quasi-neutrality conditions for densities of charged particles and for their fluxes to the reactor wall. The output parameters were electron energy distribution function (EEDF), mean electron energy and drift rate, transport and kinetic coefficients of neutral and charged species, their volume-average densities and fluxes. It was found that the dilution of HBr by any mentioned additive gas influences plasma chemistry through the electron impact kinetics due to the changes in both electron density and rate coefficients. The last results from the deformation of the EEDF and increasing mean electron energy. [Preview Abstract] |
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CTP.00021: Global model of low-pressure Cl$_{2}$/Ar inductively coupled plasma Romain Chanson, Nicolas Vaissi\`ere, Ahmed Rhallabi, Christophe Cardinaud, Marie Claude Peignon, Sophie Bouchoule Nowadays, plasma processes represent one of the keys for the integration enhancement of electronic and optical devices. Indeed, it is now possible with plasma etching process using an inductive coupled plasma (ICP) to transfer nanometer scale patterns from the mask to the substrate. The success of the high aspect ratio pattern transfer without geometrical defects (bowing, undercut, trenching,..) is tributary of a good understanding of the physical and chemical mechanisms of the plasma discharge and the surface kinetics processes. In this context, a gas phase kinetic model has been developed to study the transport of charged and neutral species created in Cl$_{2}$-Ar ICP plasma discharge. The model is 0D and it is based on the resolution of the differential equations associated to the mass balance equations of produced species in a reactor coupled to the both neutrality equation and power balance equation. The model allows to determine the densities of charged and neutral species and electron temperature as a function of operating conditions. A satisfactory agreement between the simulation and experiment concerning the electron temperature and electron density is obtained. [Preview Abstract] |
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CTP.00022: Modeling of the Advanced Plasma Source Benjamin Schroeder, Ralf Peter Brinkmann Plasma Ion Aided Deposition (PIAD) is a well-suited technique to manufacture high quality surface coatings for i.e. laser applications. We consider the Advanced Plasma Source (APS) which works below 0.1\,Pa and generates an expanding plasma beam. Due to charge exchange collisions, a secondary background plasma forms which is not in equilibrium with the background gas. By solving a simplified Boltzmann Equation for the primary ions as well as employing the continuity equation and momentum balance for the secondary ions, we derive a nonlinear differential equation for the velocity of the secondary ions. This equation shows multiple removable singularities and one (essential) bohm singularity. Solving the equations yields macroscopic plasma features (fluxes, densities, electrical field). As the ion energy distribution function plays a crucial role for the growth of the coating, we use the derived parameters in a hybrid monte carlo simulation to calculate it. The results are being compared to experiments. [Preview Abstract] |
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CTP.00023: Discharge characteristics of plasma display panel containing traces of impurity gas Yoshikuni Hirano, Akinori Oda, Keiji Ishii, Yukio Murakami To improve the discharge characteristics of plasma display panels (PDPs), we investigate the influence of an impurity gas on the discharge characteristics. Previously, we reported influence of O$_{2}$ or H$_{2}$ on the discharge characteristics of PDPs with a Ne(95{\%})/Xe(5{\%}) mixture. Meanwhile, high Xe content discharge gas is well known for improving the luminous efficacy. In this study, we investigated the discharge characteristics of PDPs with a Ne(90{\%})/Xe(10{\%}) mixture gas with oxygen. As a result, a large amount of O$_{2}$ raises the minimum sustaining voltage by reducing the wall charge, because a negative oxygen ion is slowly moved to form a wall charge. This result is similar to that obtained when using 5{\%} Xe, but differ in degree is different in the two cases. Although the wall charge at areas adjacent to the discharge gap slightly decreases when the Xe concentration is 10{\%}, the minimum sustaining voltage is relatively high in this case. Hence, a small amount of O$^{-}$ ion affects the discharge voltage when the Xe content is high. \\[4pt] [1] Y. Kamiya, Y. Hirano, A. Oda, K. Ishii, Y. Murakami, and H. Hiramoto : Proc. 16th Int. Display Workshop, p. 919 (2009). [Preview Abstract] |
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CTP.00024: Particle Simulations of Sheath dynamics in Low Pressure Capacitively Coupled Argon Plasma Discharges Yoshinori Takao, Kenji Matsuoka, Koji Eriguchi, Kouichi Ono A numerical study of low pressure parallel-plate rf Ar discharges has been performed including the transport of ions and electrons in the sheath on the substrate. We employ a two-dimensional particle-in-cell with Monte Carlo collisions (PIC/MCC) method, for an asymmetric reactor geometry with an external electrical circuit. The plasma chamber is 12.5 cm in radius (5 cm in radius for the rf-powered electrode) and 4 cm in height. The peak electron density obtained in the discharge is $2.0 \times 10^9$ cm$^{-3}$ at 20 mTorr and a rf voltage of 300 V, where the dc self-bias voltage is about - 200 V. The angular distribution function of ions (IADF) has a significant peak at around normal incidence (or at an incident angle $\theta \sim 0$ from the electrode surface normal), indicating that a large part of ions impact the electrode almost perpendicularly after being accelerated through the sheath. Increasing rf frequencies from 13.56 to 40.68 MHz results in larger distribution at lower incident angles, so that more desirable angular distribution is obtained. [Preview Abstract] |
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CTP.00025: Numerical effects in particle-in-cell simulations with Monte Carlo collisions Miles M. Turner Particle-in-cell simulations with Monte Carlo collisions are widely used in simulations of low-temperature plasma phenomena. Like all computational methods, particle-in-cell simulations exhibit numerical effects that must be controlled by appropriate choices of numerical parameters, such as cell size and time step. Such numerical effects are unphysical and will induce errors in the simulation result. In particle-in-cell simulations, the main effects are velocity space diffusion phenomena, which typically appear as unphysical heating and as distortions of the particle velocity distribution functions. It has usually been assumed that these effects are not affected by the addition of Monte Carlo collisions, but we recently showed that this is not the case. Numerical effects are in fact enhanced by Monte Carlo collisions. In this presentation, we extend this work to two-dimensional simulations, and we discuss the implications for the choice of numerical parameters for accurate simulations. [Preview Abstract] |
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CTP.00026: A new versatile approximation method for the line radiation description Sergey Gorchakov$^1$, Yuri Golubovskii$^2$, Detlef Loffhagen$^1$, Alexander Timofeev$^2$, Dirk Uhrlandt$^1$ Reabsorption of radiation in spectral lines is generally neglected in the modelling of low-pressure plasma. However, even small values of the plasma thickness cause an increase of transition probability and influence the density of radiating species. Description of corresponding phenomena follows from the solution of the radiation transport equation [1]. Since the direct solution of this equation is not possible, different approximation methods are used. This contribution presents a new approach for the description of line radiation which is based on an approximation of Biberman's transmission factor [1]. The method consists of an interpolation between the asymptotic expressions for small and large absorption. Results for the spatial distribution of the densities of excited atoms, typical plasma excitation sources and various optical thickness are presented and discussed in comparison with those obtained by the matrix method [2]. The range of applicability of developed method has been evaluated.\linebreak[4] [1] T.Holstein, Phys. Rev. {\bf72},1212 (1947); L.M.Biberman, Zh. Eksp.Teor.Fiz. {\bf17}, 416 (1947) [2] Yu.Golubovskii et al., Plasma Sources Sci. Technol. {\bf 14}, 36 (2005) [Preview Abstract] |
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CTP.00027: Modeling of the Ion Induced Secondary Electron Emission in RF PLASMAS with the PIC/MCC Method Zoran Petrovic, Aleksandar Bojarov, Marija Radmilovic-Radjenovic The effect of the secondary emission process on the characteristics of rf plasmas has been studied with PIC/MCC simulations with precise model of the ion-induced secondary electron production. Simulations were performed for a dual-frequency capacitively coupled plasma by using 1d3v PIC/MCC code [1]. In the model, as sugested by Phelps and Petrovic, the energy dependence of the yields per ion for differently treated metal surfaces have been implemented [2,3]. We have compared results for yields for the so called ``dirty'' and ``clean'' surfaces and observed the spatial profiles of charged particles and ion energy distributions. The obtained simulation results indicate that the plasma characteristics are greatly affected by the secondary emission, changing the overall parameters of dual-frequency CCP reactors especially in applications as etching devices. Overall conclusion may be that in modeling CCP an exact model of the secondary electron emission should be included, as to ensure better agreement between simulation and experiment. [1] J. P. Verboncoeur, \textit{Plasma Phys. Control. Fusion}, 47, A231, 2005. [2] A. V. Phelps and Z. Lj. Petrovic, \textit{Plasma Sources Sci. Technol, }8, R21, 1999. [3] M. Radmilovic-Radjenovic and Z. Lj. Petrovic, \textit{Europ. Phys. J.}, D 54, 445, 2009. [Preview Abstract] |
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CTP.00028: Spatio-temporal Characteristics of APD in He-Air Gas Mixture using Multi-dimensional Fluid Model Muhammad Iqbal, Miles Turner We present the characteristics of atmospheric pressure discharges (APDs) in He-air gas mixture with all meaningful chemical processes. The temporal profiles of conduction discharge current density are distinguished in the He-N$_{2}$ and He-air gas mixtures with the identification of weak and strong asymmetric breakdown mechanisms. The understanding of multi-dimensional features of bulk discharge plasma is elucidated in the breakdown phase by the spatial analysis of charge carriers (e$^{-}$, He$^{+}$, He$_{2}^{+}$, N$_{2}^{+}$, O$_{2}^{+}$, O$^{+}$, N$^{+}$, O$_{4}^{+}$, N$_{4}^{+})$. The behavior of electrons is elaborated in the passive phases, which provides the criterion for the minimum density of electrons before the evolution of next breakdown pulse. The temporal growth of different production rates shows that the charge transfer process is emerged as one of the dominant mechanism than the Penning ionization of impurities in He-air gas mixture. The considerable amount of O$^{-}$ ions is persisted in the positive column than other negative ionic species (O$_{2}^{-}$, O$_{3}^{-}$, O$_{4}^{-}$, CO$_{3}^{-}$ and CO$_{4}^{-})$, while the axial width of peak density increases from the light to heavy species near the anodic barrier. The validity of multi-dimensional fluid modelling simulation results of atmospheric pressure discharges are provided by the comparison of experimental results. [Preview Abstract] |
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CTP.00029: One dimensional modelling of XeCl barrier discharge exciplexe lamp Le Thanh Doanh, Sounil Bhosle, Georges Zissis Basing on the previous simulation models for Dielectric Barrier Discharge (DBD) lamps [1][2] and the knowledge on their boundary conditions [2] we present a one --dimensional modelling of a DBD excilamp for the mixture of Xenon and Chlorine at high pressure. The model presented here permits us to describe the space and time evolution of all species considered in the volume of the discharge when the DBD lamp is supplied with various waveforms. [Preview Abstract] |
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CTP.00030: PIC/MC simulation of electron current to spherical probe David Trunec, Zdenek Bonaventura, Petr Zikan A computer model of particle movement in surroundings of spherical electrostatic (Langmuir) probe immersed in the plasma has been developed. This model is based on Particle in Cell (PIC) and Monte Carlo (MC) methods. The model allows to calculate the electron current to the probe in the case when the collisions between electrons and neutral gas atoms occur and therefore usual probe theories are not valid. As a case study spherical probe immersed in low temperature plasma consisting of electrons and argon ions in helium buffer gas was chosen. Such plasmas are usual in flowing afterglow experiments. In this contribution calculated probe characteristics for different pressures are presented together with spatial profiles of particle concentrations and electric potential. [Preview Abstract] |
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CTP.00031: Statistical Analysis on Frequency Ocsilation Mirnov Coil in IR-TI Tokamak Shervin Saadat, M. Kazem Salem Resonant helical field (RHF) is one of the present fields in IR-T1 tokamak. RHF changes plasma mode and increases the time of plasma confinement in tokamak. Mirnov coils are the most useful diagnostics in tokamaks. In this work, the statistical analysis on frequency (SPSS) for mirnov coils data has been utilized and the effect RHF on plasma stability is studied For this purpose we define a time series on mirnov coils data and use the spectral density analysis. We show that the frequencies will be change and the plasma modes too. We can calibrate RHF {\&} feedback fields in IR-T1 tokamak and similar tokamaks [1,2]. \\[4pt] [1] G. M. Jenkins {\&} D. Watt, ``Spectral Analysis {\&} Its Applications,'' 1968.\\[0pt] [2] C. Chatfield, ``The Analysis of Time Series: An Introduction,'' 2$^{nd}$ Edition, 1982 [Preview Abstract] |
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CTP.00032: NEGATIVE ION AND DUST PARTICLE CONTAINING PLASMAS |
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CTP.00033: Modeling of the negative ion source for the ITER neutral beam heating system Nicolas Kohen, Jean-Pierre Boeuf, Gerjan Hagelaar, Gwenael Fubiani The injection of energetic neutral deuterium atoms will be one of the major heating methods of the ITER plasma. The 1 MeV, 16.5 MW neutral atom beam will be obtained by acceleration and collisional neutralization of negative ions extracted from an inductively coupled low temperature plasma source. In this paper we present the first results of a 2D fluid/hybrid model of the driver, expansion chamber and magnetic filter for an H$_{2}$ plasma, in the conditions of the ITER negative ion source. We discuss the general plasma properties: plasma density, electron and neutral particle temperatures, ion composition (H$^{+}$, H$_{2}^{+}$, H$_{3}^{+})$, dissociation degree of H$_{2}$, and the effect of the magnetic filter, in a large range of input power (10-80 kW) and source pressure (0.2-0.8 Pa). The results show a decrease of the gas density when the plasma is turned on, due to gas heating and to the neutral gas depletion induced by ionization. The low gas density leads to high electron temperature in the driver, and to saturation of the plasma density growth with power. The simulation results are globally consistent with recent experiments on the negative ion source developed at IPP Garching. [Preview Abstract] |
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CTP.00034: Higher-Density Negative-Ion Production Using Magnetized SF$_{6 }$Plasma M. Abid Imtiaz, Tetsu Mieno Negative-ion plasmas have a big potential to improve production of high-quality LSIs in the high-tech industries by reducing notching effects during Si-etching. To realize the ultra-fine etching in LSI fabrications, a higher-density and stable negative-ion source is necessary. In a magnetized plasma column generated from an electronegative gas, it is known that negative ions are accumulated around the plasma column via radial diffusion [1]. In this study, DC discharge is applied in SF$_{6}$ gas to produce a plasma column with $B= $0.3 Tesla. The Langmuir probe method is applied for the diagnosis of the plasma produced in a metal chamber of 200 cm long and 21 cm diameter. Gas pressure and discharge current dependences of $n$(-) are observed. The radial density profiles are compared with those of CF$_{4}$. Negative-ion density is calculated using the modified Bohm criterion [1]. It is found that at $p= $0.13 Pa $n$ (-) in SF$_{6}$ plasma is $\sim $8x10$^{17}$ m$^{3}$, and in CF$_{4}$ plasma, $n$ (-) $\sim $3x10$^{17 }$m$^{3}$. This ion-ion plasma has $n$(-)/$n$(e) range from 100 to 900, and is attractive for applications. \\[4pt] [1] M. Abid Imtiaz, S. Tsuruta and T. Mieno: Plasma Sources Sci. Technol. \textbf{16} (2007) 324. [Preview Abstract] |
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CTP.00035: Brownian motion of particle in a gas with non-equilibrium distribution function Sergey Maiorov, Alexander Ignatov, Sergey Trigger, Piter Schram In dusty plasma usually one supposes, that the macroparticle is in equilibrium with atoms of the surrounding gas. In the present work the kinetic characteristics of Brownian particle are found by the molecular dynamic simulations. We consider the three-dimensional diffusion with the specific behavior of the distribution function of the ``bath.'' We use for calculations the non-equlibrium distribution function of atom on velocities: \[ f_{atom} (V)=(1-\alpha )V^2\exp (-V^2/2)+\alpha V^2/(1+V^{2+n}), \] Here $V$ -- atom velocity, $\alpha $ - part of non-equilibrium ``long tail'' Earlier the case of Brownian motion of macroparticle in perfect gas has been considered. The influence of the ``long tail'' of atomic distribution function has been neglected. The results of numerical simulation of Brownian motion of charged macroparticle in constant electric field are considered. [Preview Abstract] |
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CTP.00036: Dusty Plasmas of Gas Mixtures Sergey Maiorov, Sergey Antipov, Michail Vasiliev, Oleg Petrov, Vladimir Fortov The data obtained in numerical calculations of characteristics of drift of ions and electrons in constant electric field in \textit{He-Kr} mixtures allowed us to make the analysis of the first experimental results on qualitative level. It follows: - first, at low concentration of \textit{Kr} anisotropy of interaction of dust particles, that is most strongly shown in the big difference of distances between particles in a chain and between chains at 1{\%} \textit{Kr} and low pressure, increases; this fact naturally associates with supersonic character of the ionic stream; - secondly, in \textit{He-Kr} mixtures even at very low concentration of \textit{Kr} (much less than 1{\%}) helium ions practically are not presented, also the characteristics of the ionic stream are caused by \textit{Kr} atoms; - thirdly, at a high pressure change of \textit{Kr} concentration influences more considerably on average distances between dust particles (distances between particles in chain are approximately equal to interchain distances); this fact can be connected with that circumstance that change of \textit{Kr} concentration influences on average electron energy more strongly because of the big energy inputs to \textit{He} excitation and almost total absence of its ionization. [Preview Abstract] |
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CTP.00037: A parametric study of the stratification of electronegative plasmas and the formation of ion-ion plasmas due to magnetic filtering Quentin Delivre, Ane Aanesland, Pascal Chabert A parametric study of the formation of ion-ion plasma regions at the periphery of magnetized electronegative plasmas is presented. The experiments are performed in the downstream chamber of a Helicon source and ``pure'' ion-ion plasma regions are obtained in both SF6 and in Oxygen. The experimental mapping of the ion-ion plasma formation and its dependency on neutral density, magnetic field, radial position (position perpendicular to the magnetic field) and power is compared with a recently developed analytical model. The model considers a cylindrical finite geometry with the magnetic field lines parallel to the cylinder axis, and assumes isotropic electron temperatures. A relatively good agreement between the experiments and the analytical model is obtained, but the experiments shows the importance of the electron temperature, which decreases perpendicular to the magnetic field. [Preview Abstract] |
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CTP.00038: 2D fluid simulations of two-chamber ICP electronegative plasma source Anatoly Kudryavtsev, Eugene Bogdanov, Konstantin Serditov Two-dimensional fluid simulations of two-chamber oxygen ICP sources with conductive walls are presented. The external power is applied to the first, active discharge chamber and formed plasma extends in the second, expanding chamber. It is found that in two-chamber ICP plasma sources spatial distributions of charged particles densities and fluxes are very complicated. Due to spatial inhomogeneity of the plasma density and the electron temperature, the considerable electron vortex current arises. As a result the electron transport is not ambipolar and electron flux doesn't equal to the ion ambipolar flux at any point of discharge volume. It is found that even a direction of electron flux is different in different parts of the boundary cross-section between chambers. Also shown that because negative ions are repelled by any object inserted into the plasma, probe holder strongly affects on negative ions spatial distributions. This can lead to errors in measurements of negative ions parameters by any laser photodetachment technique in its combination with probe measurements. [Preview Abstract] |
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CTP.00039: Creation of Ion-Ion Plasmas through Magnetic Filtering Dennis Gerst, St\'ephane Mazouffre The market for electric space propulsion is constantly growing and is dominated by two types of thrusters, the gridded ion engine and the Hall effect thruster. Both thrusters are propelled by electropositive plasmas with a recombination length of several hundred meters which leads to interaction and contamination of the space vehicle. A new kind of thruster has been suggested and patented by P. Chabert. The PEGASES thruster (Plasma Propulsion with Electronegative GASES) uses an ion-ion plasma, which means an electron free plasma, as propellant. The contamination of the spacecraft can be reduced drastically, due to the short recombination length between negative and positive ions. To create ion-ion plasmas it is necessary to use strongly electronegative gases such as SF6 or Oxygen. In order to create negative ions a magnetic field is used to trap and subsequently cool down the electrons so that they can attach to the neutral molecules. In this work different magnetic field configurations, as radial, axial and cusp field in various field strengths, have been investigated, in an inductive RF discharge, with the means of Langmuir probes. [Preview Abstract] |
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CTP.00040: Void Closure of Dust Cloud by Modulated-13.56 MHz RF in PK-3 plus Complex Plasmas on the International Space Station Kazuo Takahashi, Hubertus Thomas, Ralf Heidemann, Robert Suetterlin, Lenaic Couedel, Manis Chaudhuri, Gregor Morfill, Satoshi Adachi Microgravity gives the complex (dusty) plasmas where dust particles are embedded in completely charge neutral region of bulk plasma. The dust cloud of an uncompressed strongly coupled Coulomb system shows atomic model with several physical phenomena, e.g., crystallization, phase transition, and so on, which are currently demonstrated on the International Space Station. The dust particle free region (so called void) often disturbs particle distribution to form, e.g., crystal and dynamics to be observed in a physical phenomenon such as critical point. The PK-3 plus can control the particle distribution and make void close with additional bias-voltage modulating rf basis of 13.56 MHz. The electron density profile connected with potential distribution was clearly affected on by the modulated-13.56 MHz. The steep peak of electron density profile got gently down and changed in shape to be flat with modulating the basis, resulting in void closure of dust cloud. [Preview Abstract] |
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CTP.00041: Effects of rotational frequency on the growth rate of dust ion-acoustic wave in a complex plasma Myoung-Jae Lee Dust particles in a plasma are created in various situations, such as in dc discharges, rf discharges, laser-driven plasmas, and processing plasmas used in device fabrications, and in space, such as in interstellar clouds and solar systems. In general, a large number of background electrons can stick onto the surface of dust particles during the charging processes, and as a result, a significant depletion of the electron number density can occur. If the shape of charged dust particles is non-spherical, they can rotate due to the interaction with the surrounding plasmas or oscillating electric field. Therefore, a significant modification of the conventional plasma wave dispersion relations may be necessary for the complex. In this work, the growth of a dust ion-acoustic wave is investigated in the presence of the rotating dust particles in a superthermal plasma. The full spectra of the growth rate of the dust ion-acoustic wave are obtained and analyzed. The growth rate is found to be enhanced by the rotation frequency but suppressed as the number of plasma in the high-energy tail is increased. [Preview Abstract] |
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CTP.00042: Dust Formation in a DC discharge Armelle Michau, Guillaume Lombardi, C\'ecile Arnas, Xavier Bonnin, Khaled Hassouni Evidences of nanostrucutred dust particles in thermonuclear fusion rector with carbon-facing components have been reported [1]. This formation may be due to some parasitic plasmas observed in fusion reactors. The formation of particles in such conditions is investigated here using a simple laboratory DC electrical discharge. We make use of a numerical model to analyze the formation of dust through cathode sputtering and subsequent molecular growth in this discharge. The model developed for this study includes three modules. The first one describes the DC discharge in a dust-free plasma with a Monte-Carlo simulation combined with an analytical discharge models.. These profiles are then used as input data for the modules that describe growth and transport of carbon clusters and particle in the discharge column [2]. The model developed takes into account neutral and negative carbon clusters. The largest molecular edifice is assumed to give rise to spontaneous nucleation of solid particles. The third plasma module solves fort he dust total density, average mass and average charge. The average particle charging is described by a detailed charge balance where a fluctuation of the dust is also considered. \\[4pt] [1] V. Rohde, et al., J. Nucl. Mater. 313-316 (2003) 337. \\[0pt] [2] J. Bernholc, J. C. Phillips, J. Chem. Phys. 85(6, 258-3267(1986) [Preview Abstract] |
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CTP.00043: On the hydrocarbon kinetics in dust producing symmetrically driven rf plasmas Juergen Roepcke, Dmitry Lopatik, Brankica Sikimic, Frank Hempel, Mark Boeke, Ilija Stefanovic, Nader Sadeghi, Joerg Winter The chemical phenomena in hydrocarbon containing Ar/He dusty plasmas have been studied combining MIR tuneable diode laser absorption spectroscopy (TDLAS), Fourier transform infra-red (FTIR) and mass spectroscopy (MS) techniques. The experiments were done in a rf cc-coupled parallel plate reactor, f=13.56 MHz. Using TDLAS, the temporal evolution of C$_{2}$H$_{2}$, C$_{2}$H$_{4}$, CH$_{3}$, CH$_{4}$, CO and CO$_{2}$ were measured. Simultaneously, FTIR spectroscopy was used to monitor the growth process of the particles whereas MS was used to analyse the exhaust gas. The concentrations of the species were in the range of 10$^{10}$ to 10$^{14}$ molecules cm$^{-3}$. The change in plasma conditions, in particular the sudden decrease of the electron energy with the disappearance of the dust after it reach a critical size, leads to a reduced degree of dissociation of CH$_{4}$, while the density of C$_{2}$H$_{2}$ is enhanced. [Preview Abstract] |
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CTP.00044: Dust particles charge experimental evaluation in laser induced high pressure colloid plasma flows E. Yu. Loktionov, Yu. Yu. Protasov Generation of the laser-induced dusty gas-plasma flows is possible when matrix substance spectral ionization threshold is lower than dust component evaporation threshold. Such conditions are possible under action of shortwave radiation ($\lambda \sim $213 nm) on easily ablating polymeric media ((C$_{2}$F$_{4})_{n})$ containing transparent dielectric particles (SiO$_{2})$. Electron concentration in plasma (n$_{e}\sim $10$^{18}$ cm$^{-3})$ and dust particle charge (z$\sim $1,510$^{8} \quad e)$ achievable in this way enable us to carry out investigations in a previously unstudied range of parameters. The comparative analysis of the known data on the dust particle charge with those obtained in this work shows that there exists a dependence of the dust particle charge (z/R$_{d}^{2})$ on the electron concentration in plasma carrier ranged n$_{e}\sim $10$^{8}$--10$^{18}$ cm$^{-3}$, which is close to that for the power (with the exponent equal to $\sim $0.25). [Preview Abstract] |
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CTP.00045: Investigation of Negative Ion Production in an Ar/CF4 Matrix-ECR Plasma Source with Transversal Magnetic Filter Pierre Baele, Mihai Draghici, Eugen Stamate Dry etching performed in plasma discharges is a key process in micro- and nanoelectronics industry. Recently, a considerable effort was dedicated to develop negative ion sources as an alternative solution for low-damage silicon etching using negative ions instead of positive ions. Despite of this interest, no plasma source using negative ions for etching at standards required in the processing industry has been developed so far. This work is reporting on negative ion production in Ar/CF4 matrix-ECR plasma with a transversal magnetic filter. Mass spectrometry and probes are used for plasma diagnostics. A 4x3 matrix configuration of individual ECR plasma cells produced by Boreal Plasma is mounted at the top of a cubic chamber. Each cell includes a water cooled permanent magnet that provides a localized magnetic field necessary for electron cyclotron resonance. A water cooled magnetic filter is used to reduce the electron temperature. The negative ion spectrum is dominated by F- and it depends on pressure, discharge power and Ar/CF4 ratio. The density ratio of negative ion to electron was less than 3 for 3 mTorr in a power range up to 1800 W and reached 15 for 9 mTorr. Etching rates by positive ions and negative ions are reported for different discharge parameters. [Preview Abstract] |
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CTP.00046: Dust charge and potential in a two ion temperature dusty plasma Davoud Dorranian, Farideh Shahbaz Tahmasebi, Yasaman Golian Dusty plasma consists of macroscopic particles of nanometer to micrometer size immersed in a gaseous plasma environment. It can be observed by introducing a flow of molecular impurity in a double plasma device. The impurity particles will be charged quickly, while keeping relatively in low temperature. The particles typically attain several hundred or thousand elementary charges due to the inflow of plasma electron and ions. The dust particles potential and electrical charge in plasma with two ions at different temperatures is calculated. Electrical charge of dust particles is self consistently determined by local plasma electron and ion currents. It is found out that the dust particle potential is strongly affected by the mass and temperature difference of plasma ions. [Preview Abstract] |
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CTP.00047: Surface production of negative ions on different materials in H$_{2}$ and D$_{2}$ plasmas Ahmad Ahmad, Marcel Carrere, Jean-Marc Layet, Pravin Kumar, Gilles Cartry Negative ion formation by dissociative attachment on molecules in low pressure plasmas has been largely studied, whereas, negative ion formation on surfaces has been few investigated. In the present experiment, a sample is placed in the diffusion chamber of a helicon plasma reactor, facing a Hidden EQP mass spectrometer. The sample is biased negatively with respect to the plasma potential. Negative ions formed on the surface upon positive ion bombardment are repelled by the sheath and analysed by the mass spectrometer. The negative ion energy distribution functions are recorded. In a first time we have shown that under positive ion bombardment, a huge number of negative ions are produced on a graphite surface placed in low pressure H$_{2}$/D$_{2}$ plasma. The goal of the present work is to compare graphite with other materials (amorphous carbon, diamond, doped diamond, silicon{\ldots}). [Preview Abstract] |
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CTP.00048: Computer Simulation Model of Charged Nanoparticles Clustering and Powder Deposition Galina Zmievskaya, Anna Bondareva A new technology has been introduced for creation of materials and structures with special properties. The formation of nanoparticles in plasmas, the charging of nanoparticles and the first order phase transition leading to crystal formation are investigated by simulation stochastic simulation methods /SSM/. It has been applied to study of the silicon carbide 3C -polytypic model formation. SiC experimental producing has attracted considerable attention. The feasibilities of both: SSM on the base of stochastic differential equations/SDE/ and dusty plasma 3D3V kinetic object-oriented code allows to study non-equilibrium stage of charged particles clusterization in plasma and crystal powder formation as an adjunct to other methods of experiments interpretation. We assume that formation of charged clusters and evolution of their size (clustering) is to be described by kinetic distribution function /DF/ versus sizes. Here we refuse from both: idealized thermodynamics concept of phase transition as well as the Sleiozov-Lifshits exponential factor of forming a nucleus rate from classical nucleation theory. Powder of \textit{3C-SiC} DFs are non stationary, which depend on follows: Charging of melted droplets, its stoichiometric state, neutralization and coagulation on the substrate, model jump of temperature etc. [Preview Abstract] |
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CTP.00049: Dust growth in PK-4 L. Woerner, G. Wattieaux, E. Kovacevic, J. Berndt, M. Mikikian, S. Albrecht, M.H. Thoma, G.E. Morfill, L. Boufendi Dusty plasmas are a unique possibility to study the formation of nanoparticles from the gas phase in a closed and controlled laboratory setup. Particle growth is interesting regarding fundamental physics but in addition biomedical and industrial applications are under investigation. The objective of this work covers the study of dust formation in a dc discharge. The dc discharge is run inside an u-shaped glass cylinder. It is operated by two electrodes to which voltages up to 2 kV can be applied. In order to capture particles the polarity of the voltage can be switched. An rf coil is wrapped around the tube which is operated at 13,56 MHz and a peak-to-peak voltage of 200 V. The chamber is operated with Argon and mixtures of Argon with Acetylene at pressures around 100 Pa. Hence the growth is observed from etching particles laying on the surface of the glass tube, injected particles captured in the plasma, and in the gas phase by chemical reactions from Acetylene. The major prospective is to compare the growth mechanisms with those observed in experiments using rf discharges. [Preview Abstract] |
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CTP.00050: Synthesis of water ice particles in a rf plasma chamber with the cooled electrodes Satoshi Shimizu, Tetsuji Shimizu, Hermann Rothermel, Boris Klumov, Ove Havnes, Hubertus Thomas, Gregor Morfill Water ice particles are present in a long row of terrestrial and space situations. The processes which lead to the formation of ice particles especially in the troposphere and stratosphere has received considerable attention, but are still not fully understood even though this is the atmospheric region which is most accessible to in situ observations. We will describe a new type of experiment for the formation of water ice particles of sizes up to a few $\mu$m. The ice particles are created and levitated in a H$_{2}$(or D$_{2}$)/O$_{2}$ plasma chamber with the electrodes cooled by liquid nitrogen. The ice particles are produced within a second after plasma ignition. When the electrodes are warmed up, they disappear with increasing the water partial pressure in the chamber. Without plasma at oversaturated water vapor pressures, only condensation takes place on the cooled electrodes, but no visible particle formation is observed in the gas phase. In this system, plasma indeed has the effect for creating ice particles, i.e., gas decomposition and particle confinement in the plasma in which gas reactions take place. [Preview Abstract] |
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CTP.00051: Pressure-dependent negative ion mobilities in H$_{2}$O and its mixtures with Ar and N$_{2}$ Jaime de Urquijo, Ruiz-Vargas Gerardo We have used a pulsed Townsend technique to measure the mobility of negative ions of H$_{2}$O in parent gas and in the mixtures of H$_{2}$O with N$_{2}$ and Ar. The E/N range of measurement was 10-40 Td, while the partial pressure of H$_{2}$O was varied up to 18 torr. For a mixture of given composition, we have observed a well defined dependence of the mobility of the ionic species with total gas pressure. Besides, we have found that the measurement of the mobilities at a single pressure and several mixture ratios follow Blanc's law closely. These findings are indicative of negative-ion cluster formation, the sizes of which increase with the total pressure of the mixture. The identity of the drifting ions has not yet been assessed. [Preview Abstract] |
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CTP.00052: PLASMA DIAGNOSTIC TECHNIQUES |
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CTP.00053: Application of short, cold cathode dc discharges as gas analytical sensors Vladimir Demidov, Steven Adams, Igor Kaganovich, Mark Koepke, James Williamson A novel approach, leading to the development of a gas analytical sensor, based on measurements of the energetic part of the electron energy distribution function (EEDF) in the near-cathode plasma is reported here. A cold cathode, short DC discharge with conducting walls was used to measure the EEDF during the discharge as opposed to previous work in the afterglow [1]. EEDF measurements during the discharge are technically simpler and have dramatically better sensitivity than in the afterglow since temporal resolution is not required. Instead of the more common cylindrical Langmuir probe, the conducting wall is used as the electric probe resulting in a dramatic increase in probe sensitivity. The wall probe being almost flat also greatly reduces the ion current contribution to the measurements. Along with the experimental results, modeling of the discharge has also been performed. This research allows the possibility of developing a micro-analytical gas sensor operational up to atmospheric pressure.\\[4pt] [1] V. I. Demidov \textit{et al}., \textit{RSI}, \textbf{73}, 3409 (2002); \textit{Sov. Phys. Tech. Phys.}, \textbf{28}, 583 (1983). [Preview Abstract] |
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CTP.00054: Characteristics of perpendicular linear wires in magnetoplasma Andrey Yatsenko, Nikolay Gorobets Let's consider plasma, which is in a strong magnetic field. In this case the permittivity of plasma is described by diagonal tensor $\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}}\over {\varepsilon }} $ with components $\varepsilon _{xx} =\varepsilon _{yy} =\varepsilon _1 $, $\varepsilon _{zz} =\varepsilon _3 $, $\varepsilon _{ij} =0$, if $i\ne j$, where $\varepsilon _1 =1-{\omega _N^2 } \mathord{\left/ {\vphantom {{\omega _N^2 } {\left( {\omega ^2-\omega _B^2 } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {\omega ^2-\omega _B^2 } \right)}$; $\varepsilon _3 =1-{\omega _N^2 } \mathord{\left/ {\vphantom {{\omega _N^2 } {\omega ^2}}} \right. \kern-\nulldelimiterspace} {\omega ^2}$; $\omega _N$ is the Lengmur's frequency; $\omega _B$ is the Larmor's frequency; $\omega $ is the working frequency. The magnetic field is directed along axis OZ (anisotropy axis). In such plasma two thin mutually perpendicular wires of any length are located; the wires are not crossed. It is necessary to define the influence of anisotropy on the current distribution in each wire. This problem is solved by a method of the integral equations of electrodynamics. The system of the integral equations for currents is solved by a method of averaging. Is shown, that the period distribution of a current in each wire is determined by equivalent permittivity $\varepsilon _{eq} \left( \gamma \right)=\delta ^2\cos ^2\gamma +\delta \sqrt {\varepsilon _1 } \sin ^2\gamma $, where $\delta ^2=\varepsilon _3 \sin ^2\gamma +\varepsilon _1 \cos ^2\gamma $, $\gamma $ is angle between an axis of the first wire and anisotropy axis. Parameter $\varepsilon _{eq} \left( \gamma \right)$ is various for each wire, as it is determined not only by permittivity of plasma, but also orientation of in plasma. Thus, the current distribution in wires is established such, as though they work in various mediums. The received result can be used for plasma diagnostics. [Preview Abstract] |
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CTP.00055: Soft x-ray radiography based on X-pinch powered by portable pulse generator Stanislav Chaikovsky, Anton Artyomov, Anatoly Fedunin, Vladimir Feduschak, Natalia Labetskaya, Vladimir Oreshkin, Nikolay Ratakhin, Alexander Rousskikh, Alexander Zhigalin The extremely low radiation source size and x-ray pulse duration achievable with x-pinches makes them promising tool for fast backlighting imaging of short living plasmas and for non-damaged imaging of biological specimens using soft x-rays (0.3 $\div$ 10 keV). We present a low-scale portable pulse power generator with an x-pinch load especially developed for pulsed soft x-ray radiography. The generator provides a 300-kA current pulse with a rise time of 180 ns with short circuit load. The generator can be placed within a 1x1 m$^{2}$ laboratory area. Using diffraction patterns observed with x-pinch made of four molybdenum wires with diameter of 25.4 $\mu $m the x-ray source size was estimated to be 0.5-2 $\mu $m in the spectral range near 3 keV. Clear soft x-ray backlighting images of different samples with temporal resolution of 2 ns and spatial resolution of few microns at magnification up to 20 were recorded. Using this portable generator with the x-pinch load allows one to realize the x-ray backlighting technique on different installations in different laboratories. [Preview Abstract] |
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CTP.00056: Noninvasive Electrical Monitoring of Ion Current, Ion Energy, Electron Temperature, and Electron Yield Mark Sobolewski Traditional plasma diagnostic techniques that require inserting a probe into a plasma are not compatible with commercial plasma reactors and the manufacturing environment. In contrast, the radio-frequency (rf) current and voltage across a discharge can easily be measured outside the reactor, without perturbing the plasma or process. Furthermore, the waveforms of rf current and voltage contain information about process-relevant plasma properties. For example, one technique [1] has been developed which uses a numerical model of the plasma and its sheaths to analyze the waveforms and determine from them the total ion current and ion energy distributions. This method, however, assumes that the electron temperature is constant, and it neglects any emission of electrons from the electrode or substrate surfaces. To investigate errors arising from these assumptions, variations in electron temperature were measured by a Langmuir probe during fluorocarbon plasma etching of silicon dioxide films, and values for the yield of ion-induced and photon-induced electron emission were estimated. These results allow the resulting uncertainties in ion current and ion energy to be quantified. They also provide tests of how well the existing technique can be extended to also provide monitoring of electron temperature and emitted electron yield, in addition to ion current and ion energy. [1] M. A. Sobolewski, J. Vac. Sci. Technol. A 24, 1892 (2006). [Preview Abstract] |
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CTP.00057: UV LED absorption spectroscopy for pulsed plasma diagnostics Paul Bodart, Gilles Cunge, Nader Sadeghi, Olivier Joubert Broad band UV absorption spectroscopy (UVAS) is a well known technique to measure the density of small polyatomic radicals in reactive plasmas. Recently, it has been shown that by replacing the typical Xe (or D2) light sources by UV Light emitting Diodes (LED) it was possible to increase the sensitivity of this technique by an order of magnitude. We show that owing to this sensitivity gain, UVAS can be used to probe the radical's loss/production kinetics by monitoring their density in the afterglow of pulsed discharges with a time resolution of 10 $\mu $s. In the past, such measurements were feasible only by Laser Induced Fluorescence with a much more sophisticated and expensive equipment. This technique is applied to investigate the Chlorine pulsed plasma used for silicon etching. The recombination coefficient of Cl atoms on the reactor walls is first deduced from the rise rate of the Cl2 density in the afterglow. Then we show that the kinetics of SiCl and SiCl2 etch products in the afterglow is complex. SiCl is lost at high rate both by sticking on the reactor walls and by reacting with Cl2 molecules with a rate approaching the collision frequency. SiCl2 is produced from this reaction, but it is also lost by either sticking on the walls or a slow chemical reaction in the gas phase, both with small probabilities. [Preview Abstract] |
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CTP.00058: ABSTRACT HAS BEEN MOVED TO TF4.00007 |
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CTP.00059: A Physics-Based Procedure for Analyzing Langmuir Probe Data Ron Bravenec, Jianping Zhao, Lee Chen, Merritt Funk The usual method of obtaining the electron energy distribution function (EEDF) from Langmuir probes is through the Druyvesteyn relation [M. J. Druyvesteyn, Z. Phys. \textbf{64} (1930) 781], which relates the EEDF in an isotropic plasma to the second derivative of the electron current versus voltage. Not only is the resulting EEDF very sensitive to the type and degree of smoothing of the current, but it is also difficult to interpret physically. Our technique fits the current to an analytical expression derived from a physics-based model of the EEDF. A good fit lends support to the model whereas a bad fit motivates a reevaluation of the physics thought to govern the EEDF in the specific plasma. The model can depend on the plasma source, location in the plasma, input power, pressure, etc. For an RLSA (radial-line slot antenna) plasma source, we find the EEDF is well represented by the sum of two Maxwellians, one which may have a drift velocity. We present a fit to the electron current very near the top source region. We also compute the EEDF projected onto the cylindrical probe surface, which is valid for an arbitrarily anisotropic plasma [R. C. Woods and I. D. Sudit, Phys. Rev. E \textbf{50} (1994) 2222]. [Preview Abstract] |
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CTP.00060: Space and time resolved density measurements in reactive plasmas with the plasma absorption probe Marc Boeke, Carsten Selle, Joerg Winter The plasma absorption probe (PAP) is an efficient tool for the determination of electron densities, especially in reactive plasmas. The detection principle of the probe is based on active resonance spectroscopy. Active resonance spectroscopy is a method applied by many precedent researchers and used at present in diverse applications. The lack of adequate calibration constants and the occurrence of multiple absorption signals were two major drawbacks of the PAP, which are successfully overcome in this work. Design variations are tested by numerical computation and the model-based achievements are established in experiment. This redesigned PAP is optimized for the easy determination of electron densities. A dielectric cover protects the probe against the influences in reactive plasmas. Therefore, it withstands conditions where other probes are easily damageable. Space resolved measurements to achieve density profiles are easily possible. Also time-varying electron densities, for example in pulsed (dusty) plasma discharges have been measured. At present, a time resolution is achieved by 5 microseconds. [Preview Abstract] |
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CTP.00061: Atomic Hydrogen Densities in Expanding Thermal Plasmas S. Welzel, P.A.C. van Zon, R.A.J.M. van den Bos, W.E.N. van Harskamp, D.C. Schram, R.A.H. Engeln A cascaded arc produced hydrogen plasma expansion was studied by means of two photon absorption laser induced fluorescence (TALIF). In a weakly magnetised jet (up to 40 mT) a characteristic colour change from red to blue has been reported earlier. Particularly the intense plasma background radiation at the detected fluorescence transition ($H_\alpha $ line) hampers the application of a straightforward TALIF detection setup. Therefore a gated photomultiplier tube was used to measure and compare the TALIF signals under non- and weakly magnetised conditions. Results of the axial and radial H densities will be presented. [Preview Abstract] |
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CTP.00062: Effect of Irradiance on Laser-generated Aluminum Plasma Galila Abdellatif, Hisham Imam Spatial measurements of the emission spectra of laser-generated aluminum plasma were obtained using the second harmonics of a Q -- switched Nd:YAG laser at wavelength 532 nm with maximum energy of 100 mJ and pulse duration of 7 ns with repetition rate of 1 Hz. The diagnostics of the produced aluminum plasma was undertaken using imaging and spectroscopic techniques. The imaging technique provides useful information about the distribution of both the electron energy and electron density, while the spectroscopic technique gives the quantitative details of these parameters. The density and temperature of this plasma was measured at different laser irradiance. A shift of the general shape of the temperature and density profiles was observed. [Preview Abstract] |
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CTP.00063: Measurement of Nitrogen Dissociation Degree of Nitrogen Discharge Plasma by Actinometry Method with Subtraction of First Positive Band Spectrum Hiroshi Akatsuka, Kei Kuwano, Atsushi Nezu, Haruaki Matsuura Actinometry method to find dissociation degree of nitrogen molecule in a nitrogen discharge plasma is reported. The spectral lines from the excited nitrogen atom appropriate for the actinometry measurement lie in the wavelength region 742-747 nm. Their intensity is sometimes so weak that they are seriously overlapped by the first positive band spectrum (1PS) from the B-state of nitrogen molecule. We describe the method to calculate the complicated 1PS band spectrum. The fitting by the vibrational and rotational temperatures can reproduce the 1PS band spectrum. The subtraction of the calculated 1PS spectrum from the experimentally observed one can successfully extract three lines of atomic nitrogen, which enables us to actinometry measurement of nitrogen dissociation degree. Next, we demonstrate the measurement of dissociation degree of microwave discharge nitrogen plasma diluted with one species of rare gases. The nitrogen dissociation degree becomes lower with increasing the mixture ratio of Ar and Kr, while it becomes higher with He, which is attributed to the variation in the electron temperature. When we dilute the nitrogen with neon, we find marked increase in the nitrogen dissociation degree. [Preview Abstract] |
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CTP.00064: Determining plasma potential and the electron energy distribution using an rf impedance probe David Walker, Richard Fernsler, David Blackwell, William Amatucci In earlier work\footnote{ Phys. Plasmas 13, 032108 (2006)}$^,$\footnote{ Phys. Plasmas 15,123506 (2008)} using spherical probes we have demonstrated the usefulness of a network analyzer in plasma diagnostics in the thin sheath limit. The instrument returns both real and imaginary parts of the complex plasma impedance as a function of frequency for given bias voltages. To determine these quantities, an rf signal, much smaller than bias voltages, is applied to the probe by the network analyzer. Plasma impedance is determined by comparing the incident signal to that reflected from the plasma. This information can be used to determine sheath resistance, sheath density profiles and, a technique for measuring electron temperature. In the present work we focus on a method for finding plasma potential and the electron energy distribution. The rf method has general application to diverse areas of plasma investigations in the laboratory or in space. It can be used with \textit{in situ} instrumentation and can be extended to provide an estimate of sheath structure. [Preview Abstract] |
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CTP.00065: Design and Use of an Els\"{a}sser Probe for Projection of Alfv\'{e}n Wave Fields According to Wave Direction D.J. Drake, C.A. Kletzing, F. Skiff Measurement of plasma transport using probes usually requires simultaneous measurement of multiple quantities from which transport can be inferred. Particle and energy transport have received the most attention. We have designed a simultaneous fluctuating $E$ and $B$ field probe to evaluate wave Poynting flux for application to Alfv\'{e}n wave experiments in the LAPD. This new probe allows projection of measured wave fields onto Els\"{a}sser variables ($Z^{\pm} \equiv$ (\textit{E $\times $ B}$_{0})$/$\vert B_{0}\vert ^{2}\pm $ $B/$(4\textit{$\rho $}$_{0}$\textit{$\pi $})$^{0.5})$ where the time averaged background field $B_{0}$ and plasma mass density \textit{$\rho $}$_{0}$ are measured by other probes. Experiments were conducted in a singly ionized He-H plasma in the Large Area Plasma Device (LAPD) at UCLA. The results were compared with existing measurement techniques for this type of plasma in the LAPD [1]. Findings will be discussed at the conference. \\[4pt] [1] C. A. Kletzing, D. J. Thuecks, F. Skiff, S. R. Bounds, and S. Vincena, Phys. Rev. Lett. \textbf{104}, 095001 (2010). [Preview Abstract] |
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CTP.00066: High resolution measurement of silicon wafer temperature using super-continuum light on optical low-coherence interferometry Takehiro Hiraoka, Chishio Koshimizu, Takayuki Ohta, Masufumi Ito, Norihiko Nishizawa, Masaru Hori The control of the wafer temperature is important, because etch rate and etch profile are sensitive to the wafer temperature in the plasma etching. We have developed a monitoring system for temperature of each layer in multi-layered wafers using optical fiber-type low-coherence interferometer, which used Super Luminescent Diode as a low-coherent light source. In this study, we focused on the Super-Continuum (SC) light which is laser with the broad wavelength width from 1300 to 2000nm, in order to improve the accuracy of temperature and the resolution of film thickness measurements. We discussed temperature dependence on the optical path length of Si wafer using SC light source, and we compensated the wavelength dispersion of SC on Si wafer. The temperature deviation using the SC light was improved to be 0.4 degree C from 1 degree C using SLDs. We have measured temperatures of 8.55 $\mu $m-thickness SiO$_{2}$ film and Si on SiO$_{2}$/Si substrate simultaneously. [Preview Abstract] |
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CTP.00067: Plasma monitoring by transition in intensities of the forbidden atomic Oxygen spectral lines Vladimir Milosavljevic, Aleksandra Jesenko, Zoran Simic, Luka C. Popovic The intensity of forbidden atomic oxygen spectral lines at 630.0 nm, 636.3 nm, 297.23 nm and 557.73 nm to establish a threshold for actinometry is analyzed. Actinometry suffers from signal masking by molecular species due to molecular dissociation and trace gas emission. To establish the threshold for actinometry we monitor the emission of forbidden spectral lines and search for ``phase transition'' in the intensities of forbidden spectral lines. Concurrently the forbidden spectral line is used for determination of the main plasma parameters too. This work develops the method based on OES as a non invasive technique for quantifying complex chemistry which has direct application in plasma processing in semiconductor and other industries. The challenge in this case lies in the complex plasma chemistry that is commonly used in surface treatment and the constraint of applying intrusive sensors to industrial plasma reactors. These constraints make OES ideal for industrial use, however interpreting the spectra and extracting useful information is the challenge. This work is done with ICP 13.56 MHz RF plasma discharge at pure oxygen, as well at oxygen--argon--hydrogen mixture. [Preview Abstract] |
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CTP.00068: Spatial diagnostics of Hg/Ar and Hg/Xe discharge lamps by means of tomography Gita Revalde, Natalia Denisova, Atis Skudra, Janis Skudra The investigation of the spatial distribution of the emitting atoms in Hg/Ar, Hg/Xe capillary discharge lamps was performed. The spatial images of the lamps were registered and tomographic reconstruction was performed in dependence on the operating position of the lamps (vertical/horizontal) for the Hg (0.003 Torr) and buffer gase (Ar or Xe of 2 Torr) mixture. Fused silica capillary lamps were used with the length of 2 cm and inner diameter of 1 mm. The digital images of the lamps were obtained for different Hg,Ar,Xe emission lines in the visible region. The results of tomographic reconstruction of the spatial distribution of the excited Hg state $7^{3}S_{1}$ density in the Hg/Xe and Hg/Ar lamps as well as radial distribution of the emitting atoms in the level $7^{3}S_{1}$ versus radius of the capillary in dependence on working conditions will be presented. The reconstructed spatial distribution of exited Ar atoms showed more non-homogeneous structure in comparison with exited Xe atoms. [Preview Abstract] |
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CTP.00069: Optical and electric probe diagnostics in low-pressure nitrogen-argon and oxygen-argon inductively coupled discharges Tae Hun Chung, Young Wook Lee, Hye lan Lee Experiments with a Langmuir probe and optical emission spectroscopy combined with actinometry were conducted in inductively coupled rf 13.56 MHz N$_{2}$-Ar and O$_{2}$-Ar discharges under the pressures in the range of 1 - 30 mTorr and the applied rf powers in the range of 200 - 600 W. The Ar content in the gas mixture was varied from 5{\%} to 80{\%}. The effect of the Ar content on the plasma parameters and dissociation fraction was investigated. The variation of the intensities of various spectral lines was investigated. The electron energy probability function (EEPF), the plasma density and the electron temperature were measured Several methods of the evaluation of the probe I-V data were utilized. It is found that the dissociation fraction increases with the power and the Ar contents The plasma density is found to increase with the Ar content and with applied power while the electron temperature decreases with these parameters. [Preview Abstract] |
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CTP.00070: Space- and Time-Resolved Measurement of H$_{\beta }$ Emission Spectrum in Atmospheric-pressure Pulsed Microwave Plasma Azumi Kamata, Tatsuo Ishijima, Hirotaka Toyoda Atmospheric pressure plasmas have been given much attention because of its cost performance and various possibilities for industrial applications. In general, atmospheric plasmas are maintained by the short pulse DC or RF high voltages owing to prevent from arc discharges. To optimize the performance of the atmospheric pressure plasma for their applications, diagnostics and control the plasma are indispensable. Although Stark broadening of emission line is commonly used for the electron density measurement, pulsed operation may influence the line width due to the applied electric field, especially at the early stage of the plasma ignition. In this paper, temporal and spatial variations of H$_{\beta }$ spectra from an atmospheric pressure microwave plasma were measured. From the time-resolved measurement, difference of the line widths between parallel and perpendicular polarizations of the H$_{\beta }$ emission was observed at the early stage of plasma ignition, suggesting the influence of applied electric field on the H$_{\beta }$ spectra. To obtain both the applied electric field and the plasma density from the experimental result, line widths at various combinations of the plasma density and the electric field were calculated. Spatial profiles of emission spectra inside the slot antenna will also be presented. [Preview Abstract] |
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CTP.00071: Picosecond CARS System for Measurement of Electric Field and Vibrational Distribution Fuinction in Hihg Pressure Nanosecond Pulsed Plasmas Aaron Montello, Igor Adamovich, Walter Lempert, Ed Barnat, Sean Kearney Recently, Ito, et al (J. Phys. D: Appl. Phys., 43, 2010) have demonstrated the ability to measure electric field in high pressure N$_{2}$ containing plasmas by Infrared Coherent Anti-Stokes Raman Spectroscopy (CARS), with temporal resolution of $\sim $10 nanoseconds. In this poster, progress towards a new IR CARS instrument for electric field measurements, with temporal resolution of $\sim $150 psec, will be described. The instrument utilizes a broadband, modeless, psec dye laser which outputs broad spectral band output centered at near 604nm, with a full-width half-max bandwidth of approximately 7 nm. The Nd:YAG pump laser generates $\sim $150 psec duration pulses using an internal Stimulated Brillouin Scattering pulse compression cell, and is capable of 2$^{nd}$ harmonic (532 nm) output energy of up to 120 mJ/pulse. As a first example of the sensitivity of the system, Vibrational Distribution Functions (VDFs) of nitrogen in CO/N$_{2}$ CO laser optically pumped plasmas, at pressures as low as a few Torr, will be presented. An overview of planned electric field measurements in quasi-one dimensional nsec pulse discharges and in Fast Ionization Wave (FIW) discharges, in which the field profile is predicted to evolve in space and time on sub-nanosecond time scales, will also be presented. [Preview Abstract] |
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CTP.00072: Discharge dynamics of a micro-structured atmospheric pressure plasma channel Volker Schulz-von der Gathen, Henrik Boettner, Arthur Greb, Joerg Winter, Eungsoo Kim, Sung-Jin Park, James Gary Eden We report on phase and space resolved optical emission spectroscopic combined with electrical measurements on micro-structured plasma channel devices operated close to atmospheric pressure. These devices have confining structures in the range of several 10 $\mu $m and are made up of one linear discharge channel. They consist of a 50 $\mu $m deep channel of triangular cross-section etched into a silicon wafer and Ni electrodes coated at the edges of the channel as electrodes. This type of device is typically operated in rare gas at frequencies in the range of several kHz. Apart from an electrical characterisation investigations on the influence of excitation frequency on the development of pulse bursts are presented. Emission features propagating across the discharge channel are observed. Discharge dynamics are compared to those observed for micro-structured atmospheric pressure plasma arrays with discharge cavities of comparable cross-section. This work is funded by the DFG (FOR 1123 ``Physics of Microplasmas''). [Preview Abstract] |
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CTP.00073: Modeling and experimental study of molecular nitrogen dissociation in Ar -- N$_{2}$ ICP discharge Namjun Kang, Freddy Gaboriau, Andre Ricard, Soo-ghee Oh The dissociation of the nitrogen molecule in Ar-N$_{2}$ ICP discharge was studied both experimentally and theoretically. In experiments the total gas pressure is varied from 20 mTorr to 500 mTorr, and the fraction of N$_{2}$ gas is varied from 1 {\%} to 100 {\%}. To measure the absolute atomic nitrogen density the two-photon absorption laser-induced fluorescence (TALIF) spectroscopy was used. It is observed that the absolute N density increases with increasing pressure whereas the absolute N density decreases for pressure higher than 100 mTorr. The dissociation rate reaches about 0.8~{\%} at low pressure and strongly decreases with increasing pressure. With adding argon to the mixture, we observe that the dissociation rate is enhanced when going from a pure nitrogen discharge to an argon mixed discharge. To calculate the plasma parameters, a global (volume averaged) model was developed. The variation of the electron temperature and the particle densities were calculated by solving the particle and energy balance equations. The model calculations are compared with measurement results and the population and loss rates of each species are described in each discharge condition. [Preview Abstract] |
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CTP.00074: A novel current-voltage probe technique for plasma diagnostics at a rf biased electrode Mike Hopkins, Paul Scullin, Boris Dolinaj, Donal O'Sullivan, David Gahan Current-voltage probes are used to monitor the voltage, current and phase angle of the RF power used to generate a plasma or to bias a substrate. A key feature is that these sensors work in non-50$\Omega $ environments. This allows the sensor be placed post-match and make accurate measurements when the impedance phase is close to 90$^{\circ}$. Some of the most important plasma parameters for surface modification in plasma reactors are the flux and energy of ions arriving at the substrate. The ion flux is difficult to establish in deposition tools (as the plasma often deposits insulating layer) or when non-conducting electrodes are used. We report on a novel IV sensor, which is placed post-match in series with a capacitively coupled RF biased electrode. The sensor integrates the current into voltage bins. We show that the resulting characteristic represents the real current-voltage (IV) characteristic of the electrode. The measured IV trace is similar to a DC Langmuir probe trace and we determine the ion flux to the biased electrode. We compare ion flux measured with the IV probe to the ion flux determined with a calibrated retarding field analyzer (RFA) placed on the electrode. Other parameters such as electron temperature and plasma potential are calculated and compared with RFA and Langmuir probe measurements. [Preview Abstract] |
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CTP.00075: In situ plasma process monitoring of BCl$_3$ using quantum cascade laser absorption spectroscopy Norbert Lang, J\"urgen R\"opcke, Frank Hempel, Siegfried Str\"amke BCl$_3$ is used as a source gas in various industrial plasma applications. The online monitoring of its ground state concentration in the plasma process reactor is vital for an improved insight into the plasma chemistry and to increase productivity, reliability and reproducibility of the process. Quantum cascade lasers offer attractive options for the application of mid-infrared absorption spectroscopy for in situ monitoring and control of industrial processes. In this contribution we report on a compact quantum cascade laser measurement and control system (Q-MACS) combined with an infrared-fiber to allow a flexible and completely dust-sealed optical coupling to the reactor chamber of an industrial plasma surface modification system. For different process regimes the absolute concentrations of the precursor BCl$_3$ were measured in a pulsed dc discharge containing Ar/N$_2$/H$_2$ and BCl$_3$ at a pressure of 200 Pa. A synchronization of the Q-MACS with the process control enabled an insight into individual process cycles with a sensitivity of 10$^{-6}$ cm$^{-1}\cdot$ Hz$^{-1/2}$. [Preview Abstract] |
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CTP.00076: Comparative Study of RF Discharge in Neon by OES, Langmuir Probe, CR and PIC/MC Modelling Zdenek Navratil, Pavel Dvorak, Oto Brzobohaty, David Trunec A novel method of determination of electron temperature and electron density in plasma based on optical emission spectroscopy and collisional-radiative modelling was compared with Langmuir probe measurement and PIC/MC simulation. An RF(13.56 MHz) capacitively-coupled discharge in neon at 10 Pa was investigated by intensity-calibrated optical emission spectroscopy. The intensities of neon transitions between 3s\,--\,3p states were fitted with CR model to determine the electron temperature and density. Metastable density measured in absorption was used in the calculations. A good agreement between electron temperature measured by OES+CR method and PIC/MC simulation was obtained close to driven electrode. The decrease of the electron temperature going into the bulk plasma, as expected from PIC/MC simulation, was not observed in experiment. Electron density determined from the fit of absolute intensities was found to be 5$\times$ larger than the result of Langmuir probe measurement. The axial dependencies of electron density determined by OES+CR and Langmuir probe were very similar. [Preview Abstract] |
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CTP.00077: Expansion to Higher Mode in Electron Density Measurement by Microwave Resonator Probe Iji Liang, Shu Ohta, Kimitaka Kato, Keiji Nakamura, Hideo Sugai Microwave resonator probe enables electron density measurement from the observed shift in resonance frequency of U-shape antenna of length $L$ in plasma. The fundamental resonance ($m=1$) occurs at the frequency where $L$ coincides with a quarter of the wavelength. In this paper, operation of microwave resonator probe is expanded from the fundamental mode resonance to the higher mode resonances. For the given mode $m$, the electron density can be determined simply by the frequency difference between the resonance frequency $f_{pm}$ in plasma and that $f_{vm}$ in vacuum. The measurable highest density is experimentally found to be given by the plasma cutoff density corresponding to fvm. This is because the u-shape antenna is not efficiently exited in overdense plasma. On the other hand, the lowest electron density depends on the resonance broadening mainly caused by electron- neutral collisions. Use of the higher mode resonance expands a range of measureable electron density by an order of magnitude or more. Examples of the electron density measurement of surface wave plasma with use of the higher mode are presented. [Preview Abstract] |
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CTP.00078: Optical wave microphone measurement and analysis on pulsed laser irradiation to solid Fumiaki Mitsugi, Ryosuke Kozai, Toshiyuki Nakamiya, Yoshito Sonoda, Tomoaki Ikegami In the plasma process such as ablation, optical measurement technique to detect information on the interaction of laser and solid surface has attracted much interest. In this work, plasma induced shock, thermal and photoacoustic waves generated by pulsed laser irradiation were measured via optical wave microphone technique. This method has potential to detect high frequency density change of gas, liquid as well as plasma. A pulse of Nd:YAG laser (532 nm) was irradiated on Si wafer (t=0.5, 1.0 mm). The laser energy density was varied from 20 to 200 mJ/cm$^{2}$. The optical wave microphone measurement was carried out both at the laser irradiated surface and the back side of the Si changing the distance between the probe beam and the surface of the Si. The measured signal was analyzed by FFT. We could detect photoacoustic signal at the surface side and back side of the Si wafer via optical wave microphone. The piezoelectric sensing for the signal was also carried out for comparison. The signal intensity showed proportional property to the irradiated laser energy density. [Preview Abstract] |
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CTP.00079: RF-compensation method using Langmuir probe with auxiliary double probes Se-Jin Oh, Seung-Ju Lee, Chin-Wook Chung An rf compensation design using auxiliary double probes connected in parallel with a main measurement probe was developed for Langmuir probe diagnostics. This probe structure can reduce the sheath impedance of the main probe. In our probe design, the sheath capacitance of the probe can be increased and its sheath resistance can be decreased with increasing dc bias differential voltage between the auxiliary double probes. The I-V characteristics curve and electron energy distribution functions measured by our probe system had sufficient rf compensation performance in inductively coupled plasmas. [Preview Abstract] |
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CTP.00080: Absolute density measurement of SiH$_{x}$ radicals in SiH$_{4}$/H$_{2}$ microwave plasma by modified appearance mass spectrometry Toshiyuki Kuroda, Masahira Ikeda, Tatsuo Ishijima, Hirotaka Toyoda Appearance mass spectrometry (AMS) is one of well-known detection techniques for neutral radicals. In this technique, however, absolute radical densities are generally obtained by simply comparing the signal intensities between stable molecules and neutral radicals, taking the ionization cross sections of stable molecules and neutral radicals into account, resulting in under-estimation of neutral radical densities from the accurate values due to higher surface loss probabilities of neutral radicals. To avoid this problem, this study proposes a modified appearance mass spectrometry that can evaluate radical loss rates inside a differentially-pumped mass spectrometer. Decay time of neutral radicals inside the mass spectrometer is measured using a compact Piezo-chopper that is installed in front of an mass spectrometer orifice. This technique is successfully applied to the measurement of SiH$_{x}$ radicals in a SiH$_{4}$/H$_{2}$ microwave plasma. [Preview Abstract] |
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CTP.00081: Investigation by fast video imaging of the micro-discharges occurring during the PEO process Gerard Henrion, Amer Melhem, Frederic Brochard, Jean-Luc Briancon, Thierry Czerwiec, Thierry Belmonte This work aims at studying the micro-discharges (MDs) appearing consequently to the layer breakdown during the plasma electrolytic oxidation process. These MDs are not stationary and their evolution can be characterized by different time scales. In fact, depending on the variation in dielectric thickness, the electrical characteristics of the material surface change. This results in changes in the individual MD current density which affect also the discharge lifetime and distribution over the surface. The number, localization and aspect of the MDs evolve with time over the PEO treatment. Using fast video imaging allows us to determine the discharge lifetime and distribution over the sample surface. MDs do not appear over the whole current pulse since they are driven by the variation of the resulting voltage. By increasing the imaging frequency we determine that the MDs lifetime usually does not exceed 10 $\mu $s and that it ``blinks'' rapidly at the same location over the current pulse duration. [Preview Abstract] |
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CTP.00082: Comparison different optical emissions based measurements of electron densities Thomas Morgan, Shabnam Khalighi- Monfared, Lutz H\"uwel, Bill Graham The small size, restricted access and high gas densities make reliable electron density measurements difficult. As result emission-based techniques are often used. Here we compare the use of line splitting between the allowed and forbidden component of the 447.1 nm HeI emission line, the Stark broadening of the two HeI emission lines at 501.5 and 402.6 nm and Halpha and Hbeta lines to measure of electron density typical of those in a microplasma but in a more accessible plasma. The measurements were made in a plasma produced by a Q-switched Nd:YAG laser in atmospheric pressure He and He-Hydrogen gases. Emitted plasma light was dispersed in a 1m monochromator with an ICCD camera to record the spectrum. Our particular interest is in measurments at less than 1E16cm-3 corresponding to the plasma at times greater than about 5 microsecond after initiation. The results show that the density calculated values using Stark broadening using different emission lines of He agree to within 20{\%}. These measurements are systematically higher than the values from peak splitting of the allowed and forbidden peaks. The enhanced access in this system should allow us shortly to compare these measurements with those made using Thomson scattering. [Preview Abstract] |
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CTP.00083: QCLAS based in situ monitoring of low-k dielectric plasma etch processes Norbert Lang, J\"urgen R\"opcke, Henrik Zimmermann, Sven Zimmermann, Frieder Blaschta, Stefan E. Schulz, Matthias Schaller The processing of modern interlevel dielectrics using reactive ion etching with molecular plasmas becomes more complex, in particular as far as further scaling of interconnect dimensions is concerned. To overcome problems like damaged structures in dense and porous etched low-k materials, powerful plasma diagnostics with in situ monitoring capabilities are needed. Recently, it has been shown, that quantum cascade laser absorption spectroscopy (QCLAS) has the ability for online and in situ monitoring of etch processes with high sensitivity and time resolution. This contribution describes the application of a quantum cascade laser measurement system (Q-MACS) to monitor the absolute concentration of important reaction products, like SiF$_4$, CO and COF$_2$ in CF$_4$ and CHF$_3$ etch plasmas. First results will be presented discussing the properties of etch processes of different materials depending on time depended species concentrations. [Preview Abstract] |
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CTP.00084: PLASMA PROCESSING FOR PHOTOVOLTAIC APPLICATION |
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CTP.00085: Observation of Negative Ions in VHF SiH$_{4}$/H$_{2}$ Plasma Yoshinobu Kawai, Tsukasa Yamane, Yoshiaki Takeuchi, Yasuhiro Yamauchi, Hiromu Takatsuka, Hiroshi Muta, Kiichiro Uchino Microcrystalline silicon has been widely investigated to reduce production costs of solar cells. Usually VHF plasmas have been used to increase the deposition rate of microcrystalline silicon that is deposited by introducing a small amount of silane gas into hydrogen plasmas. Negative ions are produced in pure silane gas plasma. Thus, it is an important subject in solar cell development to investigate the parameters of SiH$_{4}$/H$_{2}$ plasma. A VHF plasma (frequency 80 MHz) was produced using the multi rod electrode. The gas was SiH$_{4}$/H$_{2}$ at the pressure of 70 mTorr. We examined the sheath potential as a function of the concentration of SiH$_{4}$/H$_{2}$. Measured sheath potentials agreed with theoretical ones. Then, we increased the concentration and measured the sheath potential. The reduction of the sheath potential was observed for the concentration of 30\%, which is due to the existence of negative ions. When negative ions were produced, the electron temperature increased. [Preview Abstract] |
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CTP.00086: The Effect of the Reflectance as a Si-Based Solar Cell Using the Nano-Imprint Lithography Processing Kyu-Ha Baek, Jong-Chang Woo, Dong-Pyo Kim, Kun-Sik Park, Lee-Mi Do, Joo-Yeon Kim, Kijun Lee In this paper, the results of the fabrication of nano-structured Si molds by stepper lithography and dry etching are presented. A nano-imprint system was used to reflectance the mold patterns to a PDMS layer on a Si template using the hot-plate technique. Since this polymeric nano-pattern is smaller than the wavelength of light, the effective refractive index near the surface changes gradually, and reduces the amount of reflection. As a result, the spectra of molds showed significantly reduced reflectance ($<$ 5{\%}) through the entire wavelength range at normal incidence. [Preview Abstract] |
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CTP.00087: Deposition rate enhancement of cluster-free P-doped a-Si:H films using multi-hollow discharge plasma CVD method Kenta Nakahara, Yuki Kawashima, Muneharu Sato, Takeaki Matsunaga, Kousuke Yamamoto, William M. Nakamura, Daisuke Yamashita, Hidefumi Matsuzaki, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani We have realized highly stable a-Si:H films of 4.7x10$^{15}$ cm$^{-3}$ in stabilized defect density at a high deposition rate of 3 nm/s using a multi-hollow discharge plasma CVD method by which incorporation of clusters into the films is drastically reduced [1]. To realize a-Si:H solar cells of a high efficiency, we have deposited cluster-free n-layer a-Si:H films by PH$_{3}$+SiH$_{4}$ multi-hollow discharge plasma CVD. The deposition rate sharply increased from 0.49 nm/s with increasing a gas flow rate ratio $R$= [PH$_{3}$]/[SiH$_{4}$] from 0 {\%} to 1.17 nm/s for $R$= 1.0 {\%}, then slightly increases to 1.27nm/s for $R $= 10{\%}. SiH emission intensity monotonically increases with $R$. A high surface reaction probability $\beta$ of 100{\%} for $R>$ 1{\%}, is estimated from the deposition rate. These results suggest the surface reaction rates of SiH$_{x}$ radicals are enhanced by PH$_{x}$ radicals. \\[4pt] [1] W. M. Nakamura, et al., Surface and Coating Technologies (2010) in press. [Preview Abstract] |
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CTP.00088: Characterization of an RF Power Splitter for Multi-Tile PECVD Systems Application Albert R. Ellingboe, Tomasz Michna Increasing the excitation frequency is known to enable higher deposition rates of Si films while maintaining solar cell efficiency. To circumvent wavelength effects, multi-tile systems are being developed. This technology requires more consideration be given to the power distribution, as all electrodes should be fed coherently. In particular, use of reliable, high-Q, low crosstalk, multi-port power dividers is critical. In multi-tile systems, feedback from the plasma load to the RF splitter can result in an uneven power distribution that leads to spatial inhomogeneities in plasma creation. For this reason, the PSTLD was introduced. It is a novel, coaxial, divide-by-N power splitter with differential outputs, operational in VHF/UHF bands. A comprehensive RF characterization of the splitter, along with detailed design considerations will be reported. Effects of dispersion as well as dependence on plasma load impedance will be presented. The proceeds of extensive EM modeling are going to be weighed against measurement results. [Preview Abstract] |
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CTP.00089: Combinatorial deposition of microcrystalline Si films using multi-hollow discharge plasma CVD Takeaki Matsunaga, Yuki Kawashima, Kazunori Koga, William Makoto Nakamura, Kenta Nakahara, Hidefumi Matsuzaki, Daisuke Yamashita, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Masaharu Shiratani Recently, we have developed a multi-hollow discharge plasma CVD method by which fluxes of H and SiH$_{3}$ radicals and their flux ratio on a substrate can be varied with a distance $z$ from the discharge region. In this study, we deposited Si films with different structures n a combinatorial way and evaluated $z$ dependence of the film crystallinity by laser Raman spectroscopy. Films were deposited using the multi-hollow discharges of H$_{2}$+SiH$_{4}$ (0.33{\%}) for a gas pressure $P$ Spatial profile of the deposition rate and the crystallinity significantly depend on z For $P$= 2 Torr, no films are deposited just near the discharges due to Si etching by H, $\mu$c-Si films are deposited for z= 3 - 32 mm. For $P$=6 Torr, $\mu$c-Si films are deposited in a narrow region for z= 0 - 7 mm. These results indicate that the spatial profile of the flux ratio of H to SiH$_{3}$ strongly depends on the gas pressure and a process window of microcrystalline Si films becomes quite narrow at a higher gas pressure [Preview Abstract] |
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CTP.00090: Atmospheric-Pressure Plasma Oxidation Process for Passivation of Si Surface Ze Teng Zhuo, Takayuki Ohnishi, Kazuma Goto, Yuta Sannomiya, Hiromasa Ohmi, Hiroaki Kakiuchi, Kiyoshi Yasutake Surface passivation films on Si wafers have been prepared by atmospheric-pressure (AP) plasma oxidation technique. Optical emission spectroscopy of O$_{2}$/He AP plasma revealed that SiO$_{2}$ films were obtained at high oxidation rate under the condition with high O emission intensity. From the MOS CV measurements of obtained SiO$_{2}$/Si interface, the interface state density ($D_{it})$ and the fixed oxide charge density ($Q_{f})$ were in the range of (4--20) $\times $ 10$^{10}$ cm$^{-2}$eV$^{-1}$ and (5--20) $\times $ 10$^{11}$ cm$^{-2}$, respectively. According to the model calculation on surface recombination velocity ($S)$ demonstrated that the obtained $Q_{f}$ was sufficient to significantly reduce $S$ for n-type Si with SiO$_{2}$ layer prepared by AP plasma oxidation. [Preview Abstract] |
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CTP.00091: The effect of substrate temperature on microstructure of nano-crystalline Si thin films deposited by ICP assisted magnetron sputtering at low temperature Kyung S. Shin, Yoon S. Choi, In S. Choi, Jeon G. Han The hydrogenated nano-crystalline silicon thin films were synthesized on glass substrate at low temperature using inductively coupled plasma (ICP) assisted magnetron sputtering. One-turn ICP coil was installed to dissociate the hydrogen molecules by the induced electrical field inside the chamber. According to the change of the substrate temperature, the microstructure characteristics of deposited films were investigated. [Preview Abstract] |
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CTP.00092: Alpha-gamma mode transition in a hydrogen radio-frequency discharge Sergey Abolmasov, Pere Roca i Cabarrocas Hydrogen rich radio-frequency (rf) driven discharges are used for deposition of microcrystalline silicon layers in thin film solar cells. The main issue for industrial application of microcrystalline silicon based solar cells is the relatively low growth rate of the microcrystalline silicon layer combined with relatively large thickness. In rf reactors the deposition rate is known to be an approximately linear function of the rf power density and is limited by the appearance of so-called alpha-to-gamma mode transition [1, 2]. In this study, the alpha-gamma transition in a hydrogen rf discharge has been measured in the pd range of 5-30 Torr cm. The discharge voltage, current and phase shift between them have been detected. A special design of the discharge system allowed visual detection of the discharge area, so that the average discharge current density could be determined. It is found that the current density (as well as the power density) in the alpha mode at 13.56 MHz grows slowly with pd-factor reaching a value of 12 mA/cm2 (about 3 W/cm2) at pd = 30 Torr cm prior the onset of the gamma mode. These parameters are about five-six times higher than those used in modern rf reactors [2] showing that there is still room for optimization of reactors driven at 13.56 MHz. References [1] A. Matsuda: J. Non-Cryst. Solids 338-340 (2004) 1-12. [2] A.H.M. Smets, T. Matsui, and M. Kondo: J. Appl. Phys. 104 (2008) 034508. [Preview Abstract] |
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CTP.00093: Generation of nitridated silicon particles and their thin film deposition using double multi-hollow discharges Giichiro Uchida, Muneharu Sato, Yuuki Kawashima, Kenta Nakahara, Kosuke Yamamoto, Takeaki Matsunaga, Daisuke Yamashita, Hidefumi Matsuzaki, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani Semiconductor nanocrystals have attracted much attention as materials for multiple-exciton generation (MEG) photovoltaics. Surface modification of such nanocrystals is important to make quantum well structure for efficient MEG as well as to extract photo-generated carriers from nanocrystals. In this study, nitridated silicon particles were produced by SiH$_{4}$/H$_{2}$/N$_{2}$ PECVD, where generation of silicon particles and their surface nitridation were independently controlled using two multi-hollow discharges. Thin films of nitridated silicon particles were deposited by controlling the N$_{2}$ flow rate. We observed strong photoluminescence (PL) emission in an energy range of 2.0 to 2.3 eV from the thin film, which may be explained by a quantum-confinement effect of silicon particles embedded in the thin film. [Preview Abstract] |
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CTP.00094: ION IMPLANTATION |
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CTP.00095: Description of the plasma immersion ion implantation and deposition system in Saudi Arabia Ahmed Hala A Plasma Immersion Ion Implantation and Deposition (PIII{\&}D) system is installed at KACST in Saudi Arabia. The device objective is the treatment of objects to enhance their tribological properties such as reducing wear and corrosion. The core technology of the system is a 100 kV pulser for PIII processes and a 7 KV pulser for Diamond Like Coating (DLC) processes. The system consists of a 2 m$^{3}$ vacuum chamber covered with a 0.25 inch lead shroud to shield against X-ray. The vacuum chamber is fitted with vacuum gauges. A base pressure of 10$^{-6}$ torr was attained using a cryogenic pump. A water cooled table is installed inside the chamber. The table is connected to the two pulsers. The samples are placed on the table for processing. The plasma is produced using a capacitive rf source. The source power is delivered by two race track shaped antennas. The antennas are placed parallel to the processing tables so as to provided a uniform plasma for the treated samples. The process is fully automated and PC controlled. The system is used to treat a variety of metal objects to enhance their wear and corrosion properties. [Preview Abstract] |
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CTP.00096: Stress-induced Diffusion of Nitrogen in Nitrided Stainless Steel Arvaidas Galdikas, Teresa Moskalioviene The nitrogen transport mechanism in plasma nitrided an austenitic stainless steel at moderate temperatures is explained by stress induced diffusion (non-Fickian type) model. The model involves diffusion of nitrogen induced by internal stresses created during nitriding process. For mathematical description of stress gradient induced diffusion process the equation of barodiffusion is used which involves concentration dependant barodiffusion coefficient. For calculation of stress gradient it is assumed that stress depth profile linearly relates with nitrogen concentration depth profile (from experimental observations [1]). Calculated nitrogen depth profiles are in good agreement with experimental nitrogen profiles. The diffusion coefficient D=1.68$\cdot $10$^{-12}$ cm$^{2}$/s for nitrogen in plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel at 380$^{\circ}$C was found from fitting of experimental data [2]. The dependencies of nitrogen ion current density and nitriding time on nitrogen concentration, nitrogen surface concentration and penetration depth are analyzed by proposed model. \\[4pt] [1] T. Christiansen, M. A. J. Somers, Mat. Sci. Eng. A, 424 (2006) 181. \\[0pt] [2] M. K. Lei, X. M. Zhu, Surf. Coat. Technol., 193 (2005) 22. [Preview Abstract] |
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CTP.00097: Microstructure and surface properties of silver by nitrogen ion implantation Amir H. Sari, M.K. Salem, A. Akhavan, A.R. Hojabri Ion implantation technique is a well-known technique to improve physical properties of metals and semiconductors. In the last two decades ion implantation has been used to produce new structural properties in the near surface region of metals. In this paper the effect of nitrogen ion implantation at the energy of 50 keV and doses in the range between 1e17 to 2e18 ions/cm$^{2}$ on silver substrate has been discussed. XRD analysis was used to characterize microstructure of implanted layer. The XRD results confirmed that by such implantation AgN$_{3}$ has been produced. AgN$_{3}$ with orthorhombic structure was formed on silver surface with cubic structure. RMS roughness of implanted samples have been obtained using AFM analysis and compared with un-implanted sample. By increasing the ion dose more than 1e17 ions/cm$^{2}$ RMS roughness increases while it finally drops due to sputtering effect at highest dose. Micro-hardness properties of implanted samples measured by Vickers test. The results show that by increasing the ion dose up to 1e18 ions/cm$^{2}$ hardness enhances. Finally, reflection changes at the UV-Vis-NIR region measured by diffuse reflectance accessory of a spectrophotometer. [Preview Abstract] |
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CTP.00098: Metal ion implantation and deposition by immersion in synchronous enhanced RF --driven plasma Constantin Diplasu, Agavni Surmeian, Andreea Groza, Cristian Teodorescu, Mihai Ganciu An improved ion source based on synchronous enhancement of RF-driven plasma by superimposed high voltage pulses is tested for metal ion implantation on non-metallic surfaces. The new method consists in applying supplementary very short positive high voltage pulsed discharges on a separate electrode synchronized with negative pulses applied on the target for ion implantation. By this method RF plasma density was increased with an order of magnitude shortly before applying accelerating pulses on the target. The advantages of this new method were revealed by nitrogen implanted tests on copper and brass samples [C. Diplasu, A. Surmeian, A. Groza, M. Ganciu, Surf. {\&} Coatings Techn. 203 (2009) 2858]. In this paper we compared the results obtained using the new proposed method to the metal ion implantation by immersion in classical RF plasma. It was demonstrated that using the improved ion source, the metal layer is more compact and less contaminated and a larger amount of implanted ions can be found in the non-metallic substrate. [Preview Abstract] |
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CTP.00099: Phosphine Dopant Profile Control and Optimization Using Advanced Plasma Implantation Ludovic Godet, Deven Raj, Nicholas Chamberlain, Svetlana Radovanov, George D. Papasouliotis Plasma implantation enables new fabrication options for advanced CMOS and non-planar devices. Detailed understanding of plasma-surface interactions during plasma implantation is a critical element for successful development of new applications. In the course of plasma ion implantation, ionized species present in the plasma are extracted and implanted into the wafer, and several other physical mechanisms, such as deposition, etching, and sputtering, proceed in parallel. The dopant depth profile into the substrate results from contributions of all these processes. In this study, phosphorus dopant profiles are optimized by characterizing the plasma composition and properties, and using the advanced process control features available in VIISTA PLAD$^{TM}$. [Preview Abstract] |
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CTP.00100: Formation of Carbon Nitride by Direct Low Energy Nitrogen Ion Implantation into Graphite Amir H. Sari, D. Dorranian, A. Shojaeefard The formation of carbon nitride has been intensively investigated in the last two decades due to its exceptional mechanical and tribological properties. In this paper formation of carbon nitride by low energy nitrogen implantation into graphite is investigated. Nitrogen ions with 30 keV energy and various doses ranging from 5$\times $10$^{16}$ to 3$\times $10$^{17}$ ions/cm$^{2}$ were implanted into the graphite. Existence of C$_{3}$N$_{4}$ peaks was observed in XRD results for implanted graphite samples. Raman spectroscopy also confirmed creation of C-N bonding. Atomic force microscopy (AFM) was used to obtain surface roughness, creation of grains and their evolution during nitrogen ion dose variations. In addition, optical properties of implanted samples measured by an UV-Vis-NIR spectrophotometer. A dramatically changes observed in absorption spectra of implanted samples at the wavelengths between 200 to 800 nm. [Preview Abstract] |
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CTP.00101: PLASMA-SURFACE INTERACTIONS |
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CTP.00102: Hydrophilic Treatment of Inner Surface of Polymer Tubes using Tubular Low-Pressure Plasma Seigo Takashima, Michiko Ito, Saburo Uchida, Takeshi Aoki, Michiyuki Kume Polymer tubes are widely used for the flow channel parts of gas and fluid. The inner surfaces of the tubes are necessary to have functional modification such as purity, hydrophilic property, hydrophobic property, and thin film deposition. In order to realize the inner surface modification of the long polymer tube having the inner diameter of a few millimeters, a tubular low-pressure plasma system consisted of a dielectric tube with two tubular metal electrodes was constructed. The dielectric tube is the processing object. The dielectric material was the nylon (polyamide) tube with an inner diameter of 4 mm and an outer diameter of 6 mm. The tube was surrounded with two copper electrodes with a length of 25 mm. The distance between two electrodes was 13 mm. RF power at 13.56 MHz was applied to the electrode. The other electrode was grounded. We demonstrated the hydrophilic treatment of the inner surface of the tubes employing the system with Ar gas. At a pressure of 100 Pa, an RF power of 40 W, and a discharge time of 5 s, the contact angle of water drop on the inner surface of the tube decreased from 80$^{\circ}$ to 0$^{\circ}$. [Preview Abstract] |
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CTP.00103: Regeneration of inorganic sorbent surfaces using dielectric barrier discharge Paul Gravejat, Frederic Thevenet, Olivier Guaitella, Antoine Rousseau Inorganic adsorbing materials are used for volatile organic compound (VOC) removal and subsequently indoor air purification. Authors focused on the regeneration of saturated adsorbing materials using surface dielectric barrier discharge exposure. Two main objectives are targeted: (i) oxidation of the adsorbed VOC; (ii) regeneration of the sorbent surface for further adsorption. Isopropanol is used as model VOC and TiO$_{2}$ thin film as model inorganic sorbent. First, adsorption properties of TiO$_{2}$ are characterized under dry and wet (RH=50{\%}) air. Secondly, regeneration of the surface is investigated as a function of various parameters: (i) input power; (ii) nature of the gas stream (air, O$_{2}$, N$_{2})$; (iii) relative humidity. By-products and reaction intermediates formed during the regeneration process are monitored on-line by FTIR. The nature of the by-products and the process efficiency is discussed according to the process parameters. Carbon balances of the process are discussed. [Preview Abstract] |
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CTP.00104: Fabrication of nanostructured black metals by use of self-growing helium bubbles Shin Kajita, Tsubasa Saeki, Yuki Hirahata, Miyuki Yajima, Noriyasu Ohno, Reiko Yoshihara, Naoaki Yoshida Helium irradiation to metals leads to the morphology change in nanometer scale by the formation of helium bubbles. It is revealed that the morphology change significantly alters the light absorption, and consequently, forms blackened metals. From the detailed TEM (transmission electron microscope) investigation with FIB (focused ion beam) technique, it was revealed that the morphology change was caused by the self-growing helium bubbles in the surface region. After various metals including tungsten, titanium and SUS surfaces are exposed to the helium plasma in a linear plasma device, the total optical reflectance decreased significantly by more than an order of magnitude. Particularly, for W, the optical reflectivity decreased two orders of magnitude, making it the darkest man-made tungsten, which could be used in high temperature circumstances. The results indicate that the helium irradiated metals can be a good medium for light absorber. [Preview Abstract] |
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CTP.00105: Effect of RF plasma treatment on the nonlinear refractive index and susceptibility of PVC film Davoud Dorranian, Yasaman Golian, Farideh Shahbaz Tahmasebi, Morvarid Rashidian Effect of argon plasma treatment on the nonlinear optical properties of red lake doped commercial PVC film is studied employing different optical techniques. PVC films were exposed to low pressure plasma from 5 to 15 minutes. Experiments were performed using the second harmonic of a continuous Nd-Yag laser beam at 532 nm wavelength and 20 mW power. The optical bleaching behavior of samples was investigated by measurement of transmission through them. For all pristine and plasma treated samples optical bleaching started at laser beam power of 3.5 mW. The nonlinear refractive index and two photons absorption coefficient of plasma treated samples were measured using Z-scan method. Experimental results show that real and imaginary parts of nonlinear susceptibility decrease with increasing the time of treatment. [Preview Abstract] |
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CTP.00106: Real time monitoring of the atmospheric-pressure low-temperature argon plasma treatment to the PEDOT:PSS Hajime Shirai, Tomohisa Ino, Tasuya Hayashi, Ryo Ishikawa, Keji Ueno We demonstrate the effect of atmospheric-pressure low-frequency plasma treatment of argon to the 3, 4-polyethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) layer on the performance of copper phtalocyanine/C60 hetero-junction solar cells. The efficiency was improved up to 0.93{\%} by adjusting the plasma exposure period, which originate from the decrease in the series resistance and the increase in the shunt resistance in the diode. The Fourier-transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) characterization revealed the PSS component contributing to high resistivity was reduced preferentially rather than the PEDOT by the plasma exposure, which reduced the sheet resistance. The effect of the Ar plasma treatment to PEDOT:PSS on the performance of the CuPc/C60 hetero-junction solar cells is discussed with the real time monitoring of the surface chemistry of PEDOT:PSS using a spectroscopic ellipsometry. [Preview Abstract] |
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CTP.00107: Chemical Sputtering Yield as a Function of Ion Incident Angle in Wurtzite-Type GaN Crystal Kenji Harafuji, Katsuyuki Kawamura A molecular dynamics simulation has been carried out to investigate the sputtering yield of wurtzite-type GaN (0001) surface with Cl-adsorbed layer. Sputtering yields of Ga and N are 0.3-0.4 and 0.1-0.15 at the incident Ar energy of 250 eV, respectively. The sputtering yield shows only a weak dependence on ion incident angle for the range of 60 to 90 degrees, whereas the yield increases as the ion incidence is more inclined for GaN surface without Cl-adsorbed layer. Ga is sputtered in the form of Ga-Cl$_{2}$, and sometimes in the form of Ga-Cl, Ga-Cl$_{3}$, and Ga$_{x}$N$_{y}$Cl$_{z}$. These products escape from the surface in the time range mainly of 200-500 fs after the impact of incident Ar ion. There are small amount of products escaping in the time range of 500-5000 fs. Single N atom is physically sputtered within 100 fs after the Ar incidence, whereas Ga is not singly sputtered. [Preview Abstract] |
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CTP.00108: Design of a microwave low-temperature plasma reactor used for simulating plasma interactions with mixed materials targets Guillaume Lombardi, Ligia Colina Delacqua, Michael Redolfi, Armelle Michau, Xavier Bonnin, Dominique Vrel, Khaled Hassouni We have developed a low-temperature plasma reactor to simulate some of the plasma/surface processes occurring under the divertor dome of tokamaks, with an emphasis on mixed materials targets and dust production. We wish to address issues related to the chemistry of erosion products, along with transport, and redeposition in parasitic plasma environments, as expected in ITER. We detail the design steps to build the plasma source using a new multi-bipolar ECR source technology, with plasma ignition through pencil sources arranged in a circle, providing for an elevated electron temperature and sustained plasma density. Two erosion targets, located above and below the sources, are exposed to the plasma. These targets types are considered: 1/ Pie-shaped multiple sectors of single material (C, W, and/or a Be-like element); 2/ Single sector made up of a suitable alloy; 3/ A tungsten or carbon blank on which powder samples of mixed materials have been deposited. These latter samples are to be obtained by mechano-synthesis (stoichiometric compositions out of chemical equilibrium). [Preview Abstract] |
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CTP.00109: Study of surface processes in N$_{2}$-O$_{2}$ plasmas Carlos D. Pintassilgo, Vasco Guerra In this work we present a theoretical study of the role of surface kinetics in N$_{2}$-O$_{2}$ plasmas. For this purpose, we have considered a low-pressure pulsed discharge in air produced in a pyrex tube and the corresponding afterglow, by coupling a kinetic model for the gas phase with a mesoscopic kinetic model to describe the heterogeneous reactions that may occur as a result of the plasmas interaction with the wall. While the gas phase model includes the interplay of different kinetics (electrons, vibrations, metastables and ions), the surface model takes into account adsorption in physisorption and chemisorption sites, thermal desorption, surface diffusion of physisorbed atoms, and both Langmuir-Hinshelwood and Eley-Rideal recombination mechanisms. Our research will report on the relevant populating mechanisms of NO, resulting from both gas-phase and surface reactions. A special attention will be given to specific operating conditions (pressure, gas input power, etc) where surface processes play a relevant role. Model results will be compared to recent measurements of heterogeneous production of this species under plasma exposure. [Preview Abstract] |
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CTP.00110: Irradiation of High Energy Electrons onto GaN Thin Films and Observation of Induced Optical Luminescence in Inductively-Coupled Plasmas Keiji Nakamura, Ying Guo, Junsi Gao, Yoshitaka Nakano, Hideo Sugai This paper reports observation of optical fluorescence of GaN thin films in an inductively-coupled plasmas containing energetic electrons with an energy higher than several keV. Such high energy electrons are produced by sheath acceleration of secondary electrons induced by ion bombardment at a negatively-biased electrode. A current of a Langmuir probe located in such a plasma is investigated to examine how the high energy electrons behaves in the plasma. It was found that a step-like increment of probe current observed immediately after the negative high voltage application was proportional to discharge power, but slightly depended on the pulse target voltage. A sample of undoped GaN film was observed to emit significant optical fluorescence in the wavelength range of 370-390 nm corresponding to band gap energy of the GaN when the plasma contains the high energy electrons, the fluorescence intensity of the GaN film increased with the incident electron energy higher than a critical energy of $\sim $5 keV. These results suggested cathode luminescence technique will be used to detect a damage density of GaN substrate surface even in plasma environment. [Preview Abstract] |
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CTP.00111: Substrate temperature effects on amorphous carbon deposition process during acetylene plasma, investigated infrared spectroscopy Kojiro Hara, Taka-aki Kawakami, Masanori Shinohara, Yoshinobu Matsuda, Hiroshi Fujiyama Amorphous carbon film has been widely used in a lot of fields. Acetylene plasma is often used for the film deposition, because the acetylene plasma can enhance the deposition rates. However, the detailed deposition mechanism has not been understood. We have investigated the film deposition process during acetylene plasma, using infrared spectroscopy in multiple internal reflection geometry (MIR-IRAS). In this paper, we investigate the substrate temperature effects on the surface reaction during acetylene plasma. Infrared spectral shapes were changed with the increases of the substrate temperature; the intensity ratio of the peak due to sp3-CHX (X=1, 2, 3) components to that due to sp2-C components was increased with the substrate temperatures. It indicates that the conversion of sp2-C components to sp3-CHX was increased with substrate temperatures. It also indicates that owing to substrate heating, the carbon clusters decreases its intensity in the film. [Preview Abstract] |
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CTP.00112: Laser-plasma induced copper surface phenomena Davoud Dorranian, Fatemeh Heydari, Mohammadjavad Torkamany, Jamshid Sabbaghzadeh In this paper, the characteristics of bulk copper surface ablated by 1064 nm Q-switched Nd:YAG laser have been studied in atmospheric air. The parameter of generated plasma is studied using the plasma emitted lines in the range of 200 to 600 nm wavelength. Width and dept of holes on the surface target are considered in different laser pulse energy. Formation of large scale structure on the surface of copper target due to Kelvin-Helmholtz instability was discussed in detail. Furthermore, the formation of copper oxide and changes in surface topology of the target were investigated by means of metallographic and SEM images. The spectroscopic and microscopic observation, illustrate the direct dependence of CuI density and ablation depth on the applied pulse energy. [Preview Abstract] |
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CTP.00113: Interference Effects in Surface-Plasmon Interaction due to the presence of External Charged Particles in Nanostructures Juana Gervasoni In this work we study the interferences and resonances arising in plasmon surface excitation due to the interaction of external charged particles with nanosystems of different shapes and materials. The obtained dispersion relations are very sensitive to the chosen dielectric functions, and so are the quantities derived from them. We show the similarities and differences among them, as well as with planar surfaces. We demonstrate that these effects interference effects must be taken into account for the design of electronic devices of nano dimensions. [Preview Abstract] |
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CTP.00114: Carbon dust particles generated due to H$_{2}$ plasma-carbon wall interaction Hiroshi Miyata, Katsushi Nishiyama, Shinya Iwashita, Hidefumi Matsuzaki, Daisuke Yamashita, Giichiro Uchida, Naho Itagaki, Kunihiro Kamataki, Kazunori Koga, Masaharu Shiratani, Naoko Ashikawa, Suguru Masuzaki, Kiyohiko Nishimura, Akio Sagara Formation of dust particles due to plasma-wall interaction has attracted much attention because dust particles can contain a large amount of tritium and may deteriorate plasma confinement in fusion devices. Therefore, it is important to reveal their formation and transport mechanisms. Experiments were carried out with a helicon plasma reactor at Kyushu University and the Large Helical Device at NIFS. Hydrogen helicon plasmas were generated by applying rf voltage to a helicon antenna. Dust particles collected using Si substrates of grounded, floating. Three kinds of dust particles, spherical ones, agglomerates, and flakes, were collected on the grounded substrates both in the helicon plasma reactor and in LHD, whereas two kinds of dust particles, spherical ones and flakes, were obtained on the floating substrates in LHD. Substrate potential may affect transport and sticking of dust particles. [Preview Abstract] |
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CTP.00115: Effects of Photoemissions in UV and VUV Regions on Nano-Surface Strucures of Soft Materials during Plasma Processes Ken Cho, Kosuke Takenaka, Yuichi Setsuhara, Masaharu Shiratani, Makoto Sekine, Masaru Hori Plasma processing of soft materials are expected as key technologies for fabrication of next-generation devices including flexible electronics, thin-film photovoltaic cells, and advanced ULSIs (low-k interlayer and EUV lithography). As one of the effective plasma sources for these processing, inductivity-coupled plasma (ICP) sources have been developed with multiple low-inductance antenna (LIA) modules, which allowed low-voltage operation of high-density ICPs [1]. For successful fabrication of these next-generation devices, it is of great significance to control nano-surface structures on the basis of understanding plasma interactions with soft materials. This presentation reports nano-surface structures of polymers during plasma processes for investigation of morphologies and chemical bonding states due to exposure with photoemissions in vacuum ultraviolet (VUV) and ultraviolet (UV) regions from the plasmas. The depth analysis of chemical bonding states was carried out via conventional x-ray photoelectron spectroscopy (XPS) and hard x-ray photoelectron spectroscopy (HXPES) at the national synchrotron radiation facility SPring-8 of the Japan Synchrotron Radiation Institute. [1]Y. Setsuhara, et al., Surf. Coat. Technol. 174-175, 33-39 (2003). [Preview Abstract] |
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CTP.00116: \textit{in situ} Electron Spin Resonance Study for Plasma-Surface interactions Kenji Ishikawa, N. Sumi, A. Kono, H. Horibe, K. Takeda, H. Kondo, M. Sekine, M. Hori Using an \textit{in situ} electron-spin-resonance (ESR) technique, dangling bond creation processes were studied. To understand both gaseous reactive species and surface reaction mechanism on the surface, creation of radicals is indeed a key process. In this study, we studied the real defect state on the surface during plasma processes. An ESR system was connected with plasma discharge tube. Both gaseous and surface radicals can be detected \textit{in situ }simultaneously. For instance, on fluorocarbon polymer, carbon dangling bonds were created by exposure of hydrogen atom (detected by ESR) transported through glass tube at down-flow of plasma. Those signals were assigned CF$_{2}$-*CF-CF$_{2}$ (hyperfine interaction of 91 and 34 G). As demonstrated, the \textit{in situ} ESR technique provides a new experimental approach to the microscopic understanding of chemical reactions on surfaces with gaseous radicals during plasma processes. [Preview Abstract] |
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CTP.00117: Surface Modification of Metals by HV Impulse Discharges in Air and Liquid Kanji Shibagaki, Masaki Ibayashi, Atsuto Mori, Takaya Hattori, Masayuki Ishida Observations of surface morphologies of metal targets irradiated by HV impulse discharge plasmas are presented. The plasmas were generated by applying standard HV impulses to rod-plate electrodes, and irradiated on the target under both atmospheric condition and liquid environment. The plasma-treated samples were characterized by SEM-EDX and XRD. When the HV impulse discharge plasma was irradiated to titanium target in air, the detailed SEM analysis showed clearly that there were many small cracks and holes on the center of the irradiated area. The repetitive HV impulse plasma irradiation at short distance between the electrodes led to synthesis of metal particles with diameters of few micrometer in a circle on the target surface. On the other hand, the surface morphology became smooth significantly after the HV impulse plasma irradiation in distilled water. On the basis of the difference in surface morphologies observed in various discharge conditions, the basic mechanisms of the interactions between the HV impulse plasma and the solid metal are discussed. [Preview Abstract] |
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CTP.00118: HIGH PRESSURE PLASMA |
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CTP.00119: Development of Atmospheric Pressure Plasma Jet with Slit Nozzle for large area treatment Nobuaki Oshima, Ryuji Takada, Tamio Hara Atmospheric pressure plasma jet has been used widely for surface treatments such as modifications, cleaning and deposition of thin films. In our previous work, a long flame nitrogen plasma jet was developed by eliminating oxygen from the atmosphere surrounding the jet. The long flame plasma jet could be applicable for treating objects having deep channels or large surface areas. Processing width of plasma jet, however, are limited to a narrow width of less than 10 mm. A large area processing capability is therefore desirable to expand the range of application in the industry including installation of plasma jets in production lines. In the present study, a wide-flame nitrogen plasma jet with a slit-type nozzle has been developed for treatment of large surface area, which is not necessary to control an ambient gas. The contact angle of water on the surface of polyethylene (PE) has been measured to estimate the plasma width expanded by the slit nozzle. It has been confirmed that contact angles of water on the polyethylene (PE) surface treated by the nitrogen atmospheric plasma jet has good uniformity in the range of 50 mm. [Preview Abstract] |
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CTP.00120: Investigation of the development of a pulsed positive discharge in micrometer size confined dielectric geometries P. Le Delliou, P. Tardiveau, P. Jeanney, F. Jorand, S. Pasquiers The development of a pulsed positive corona discharge in micrometer size confined dielectric geometries is investigated. The aim of this work is to understand how the plasma can develop inside confined geometries, representative of catalyst media in plasma enhanced catalysis applications. The reactor geometry is a point to plane one with a tungsten tip of 50$\mu$m diameter. The applied voltage ranges from 8kV to 18kV and is applied during 20ns. Time resolved imaging diagnostics coupled to microprobes current techniques are used to characterize the propagation either in transparent media (glass capillaries), or in opaque media (alumina). Round capillaries of inner diameters from 75$\mu $m up to 2mm and ``hybrid'' shapes such as rectangular tubings or square tubings are investigated. Discharge mean velocities are derived and in the case of capillaries, a maximum is found for a 200 $\mu $m inner diameter whatever the applied voltage. Discharge optical emission gets more homogeneous with smaller diameters; a tubular shaped propagation develops for intermediate capillaries and filamentary discharges are observed for larger ones. In the case of hybrid shapes, the propagation seems to be enhanced at the edges of the tube. Dielectric surfaces effects on ionization and recombination processes are considered to interpret these results. [Preview Abstract] |
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CTP.00121: Energy release of a nanosecond pulse corona discharge in atmospheric air-propane mixtures for ignition purposes S. Bentaleb, P. Tardiveau, N. Moreau, F. Jorand, S. Pasquiers One growing topic of interest in non-thermal plasma field is the use of pulsed corona discharges for car engine ignition. The purpose of this work is a better understanding of the physical mechanisms implied in the ignition of lean mixtures of air and hydrocarbons at high pressure using nanosecond range discharges. Such kind of discharges could improve the energy release in the mixtures, promoting the creation of radicals and excited species instead of direct heat, and the ignition efficiency. A positive high voltage (40-50kV) is applied between a pin electrode and a grounded plane over a short nanosecond range pulse (10-15ns). The energy of the discharge can be modified by changing the voltage and the pulse duration pulse. The diffuse regime which is observed at 1bar in pure air disappears in mixtures with propane and the discharge becomes filamentary. Although the discharge remains generally cold, the ignition of a stoechiometric air-propane mixture at 1bar by a single pulse and self-sustained flame propagation are possible. Compared to the classical car spark plug ignition which occurs in a very small volume, the single nanosecond pulse discharge can ignite a mixture all along a plasma channel, i.e. more than 1cm, and give a cylinder-shaped flame kernel. For comparable energy release, the whole volume can be burnt faster. [Preview Abstract] |
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CTP.00122: Plasma dynamics, pattern formation and streamer development during microwave breakdown Bhaskar Chaudhury, Guo-Qiang Zhu, Jean-Pierre Boeuf Filamentary plasma structure formation and self-organization during microwave breakdown in the millimeter range (110 MHz) at atmospheric pressure in air are investigated using a two-dimensional computational model. Maxwell's equation coupled with plasma fluid equations are numerically solved and compared with the experimental results of Hidaka et al., Phys. Plasmas 16, 055702 (2009). The plasma model is based on a simple, quasi-neutral diffusion-ionization equation with an effective diffusion coefficient equal to the free electron diffusion coefficient at the plasma edge and to the ambipolar diffusion coefficient in the plasma bulk (Boeuf et al. Phys. Rev. Lett. 104 015002 (2010)). The model predicts the formation of patterns that are qualitatively similar to those seen in the experiments, and that propagate toward the microwave source with velocities that are in excellent agreement with the experiments. We discuss the physical parameters controlling the propagation speed of the plasma front, the maximum plasma density that is reached in the filaments, and the shape of the observed patterns. We show that the structure of the plasma pattern in these conditions is very sensitive to the value of the electron-ion recombination coefficient. [Preview Abstract] |
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CTP.00123: Influence of molecular additives on the propagation of plasma bullets generated by microjets Claire Douat, Michel Fleury, Vincent Puech Non thermal atmospheric pressure plasma jets have recently been developed to induce surface modifications and biomedical applications. It was shown that for many device configurations, the jets consisted of plasma bullets propagating at high velocity. While most of the studies were performed with He as a feeding gas, the reactivity of the bullets could be enhanced by introducing into the feeding gas some molecular gases. In this paper, the influence of those additives on the plasma bullets properties will be reported. The microjet investigated here (300 $\mu $m in diameter) is produced by a surface DBD composed of a dielectric tube on the faces of which metallic electrodes are glued. The gases are flowing through the inner electrode which is powered by nanosecond pulsed high voltage generator. The feeding rare gases were He, Ne and Ar, while the additives were N2, O2 and synthetic air. The plasma bullet properties were analysed by correlating the electrical parameter, the emission spectra and the images of the bullet position detected with an ICCD with a temporal resolution of 2 ns. It will be shown that the shape, the propagation distance and the velocity of the bullets are sensitive function of the gas flow, of the gas mixture composition, of the applied voltage. For each rare gases, the maximum percentage of additives still allowing the generation of plasma bullets have been determined. [Preview Abstract] |
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CTP.00124: Dielectric Barrier Discharge and a Microwave Cavity Discharge in Synchronous Operation Milka Nikolic, Svetozar Popovic, Robert Leiweke, Biswa Ganguly, Leposava Vu\v{s}kovic We describe a system consisting of two discharges, a dielectric barrier discharge and a microwave cavity discharge, acting simultaneously as a tandem in pulsed repetitive regime, with controllable space, time, and power distribution. The two discharges interact by providing lower breakdown conditions, modified gas flow composition, and a more efficient production of chemically active species. We demonstrate modification of the downstream microwave discharge, its operation up to near-atmospheric conditions at limited power density, with extended post-discharge region. The operation of two discharges is exemplified by the optimized generation and sustaining of metastable oxygen in He/O$_{2}$, Ar/O$_{2}$ mixture. Metastable oxygen is monitored during discharge and in the post-discharge by time-resolved detection of selected emission bands. Intensity of the emission bands in the post-discharge allowed for determining the rotational temperature, and also for estimating the concentration of the O$_{2}$ excited species. [Preview Abstract] |
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CTP.00125: Study of a microwave plasma torch K. Gadonna, O. Leroy, C. Boisse-Laporte, P. Leprince, L.L. Alves The axial injection torch (AIT) [1] produces high-density plasmas ($\sim $1 cm length and 1 mm radius) by coupling a flowing gas (a few L/min at atmospheric pressure) to microwave power (500-900 W) at 2.45 GHz frequency. Our study is about both experiment and modeling of an AIT running in helium, to understand the distribution of its electromagnetic field, the flow of the gas/plasma system, and the plasma-to-gas heat transfer. Modeling wants to describe the gas/plasma system in terms of its density, velocity and energy, by coupling three calculation modules: (i) electromagnetic (3D), which solves Maxwell's equations considering the permittivity of the different media; (ii) hydrodynamic (2D), which solves the Navier-Stokes' equations for the gas/plasma system; and (iii) plasma (1D), under development still, which solves the fluid-type equations for the plasma electrons and ions. Experiments have a double purpose: to obtain input data for the model and to validate its results. Optical emission spectroscopy diagnostics allow obtaining the electron density and temperature ($n_{e}\sim $5x10$^{14}$ cm$^{-3}$, $T_{e}\sim $2x10$^{4}$ K), and the gas temperature ($T_{g}\sim $3x10$^{3}$ K). \\[4pt] [1] M. Moisan, G. Sauv\'{e}, Z. Zakrzewski, J. Hubert, Plasma Sources Sci. Technol. 3, 584 (1994) [Preview Abstract] |
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CTP.00126: Development of Damage-Free Multi-Gas Plasma Jet Source and Measurement of Fundamental Properties Hideyuki Hirai, Ryota Sasaki, Toshihiro Takamatsu, Moe Shibata, Masaki Ichikawa, Hidekazu Miyahara, Akitoshi Okino In recent years, atmospheric plasma jet sources have been attracted attention because of its usefulness for surface treatment or sterilization. However, conventional plasma jet sources have some limitations in the plasma gas spaces and problem of irradiation damage for target surface such as thermal or electric discharge damage. In our research group, damage-free multi-gas atmospheric plasma jet source was developed. The plasma source can generate stable atmospheric plasma jet with helium, argon, oxygen, neon, nitrogen, carbon dioxide, air and their mixed gases. This plasma source is damage-free which means low temperature of the flowing plasma gas and no risk of discharge damage to the target materials. Therefore, it is possible to be applied for not only plastic or silicon wafer but other every material such as paper, textile, metal, bio material and also human skin. The plasma source is very small and light weight. It is 83 mm long and 160 g. The fundamental properties of the plasma jet by shape and material of electrode, power supply, gas species and gas flow rate were measured. And we applied this plasma source for surface treatment and sterilization. Detailed properties of the plasma source and application results will be presented. [Preview Abstract] |
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CTP.00127: AC Driven Micro-hollow Discharges Triggered by Self-generated Dielectric Barrier Discharges Jun Watanabe, Akihisa Ogino, Masaaki Nagatsu Atmospheric-pressure discharges have been widely investigated to develop low temperature materials processing techniques for a variety of industrial applications. Up to now, several methods have been developed to generate atmospheric pressure plasmas, such as dielectric barrier discharge (DBD), micro-hollow discharge (MHD), and plasma jet. In our previous research, we studied the discharge characteristics of MHDs with a multi-hole structured DBD as pre-ionization source. We confirmed that MHDs were generated at a voltage about 500 V lower than that in the case of without DBD. From the numerical analysis, we showed that electrons generated by DBD were accelerated inside the hole by electric field applied during the negative polarity of DBD driving voltages. In this study, we focused on the MHD triggered by the self-generating DBD. To confirm that MHDs will be pre-triggered by DBDs driven by AC high voltages, we have carried out the measurements of discharge characteristics by using time-truncated sinusoidal wave signals with two periods and single hole MHD electrode. From the experiments, we confirmed that MHD was triggered at the timing of self generating DBDs. [Preview Abstract] |
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CTP.00128: Spatial and time resolved optical emission spectroscopy of Ar/NH$_{3}$ dielectric barrier discharge Petr Kloc, David Trunec, Hans-Erich Wagner, Zdenek Navratil, Gleb Fedoseev Dielectric barrier discharges (BD) at atmospheric pressure have great potential mainly for material surface treatment. The two distinctive forms of BD exist. One is characterized by large number of distinctive spatially bounded microdischarges. The other requires special conditions to operate and is characterized by spatially homogeneous discharge. Such discharge can be observed in the mixture of argon and ammonia. This work presents study of BDs in argon with different ammonia additions (0-10\,vol\%). The discharges were investigated by the Cross Correlation Spectroscopy (CCS). The observed propagation of streamer in discharge is presented. When compared to discharge in pure argon the streamer velocity is decreased for 0.1\,vol\% ammonia admixture. With increasing ammonia concentration the streamer velocity increases again. The behaviour of impurity spectra in the discharge was also investigated. [Preview Abstract] |
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CTP.00129: Study of atmospheric pressure radiofrequency Ar/O$_{2}$ plasma afterglow used for PTFE surface modification Corinne Duluard, Thierry Dufour, Emile Carbone, Fran\c{c}ois Reniers Polytetrafluoroethylene (PTFE) is a hydrophobic polymer, the surface energy of which can be tailored by plasma treatment to increase its adhesion properties or to enhance its hydrophobicity, for example for biocompatible applications. Superhydrophobic behavior was obtained by low pressure O$_{2}$ plasma treatment, and was attributed to surface roughening due to strong etching by O$_{2}$ plasma. Recently, an increase in hydrophobicity has also been observed after treatment in the afterglow of an atmospheric pressure radiofrequency Ar/O$_{2}$ plasma with up to 0.1{\%} O$_{2}$ in the feed gas. To get a better understanding of the mechanisms responsible for PTFE surface modification, the Ar/O$_{2}$ plasma afterglow is characterized by spatially resolved optical emission spectroscopy and mass spectrometry. The influence of gas flow rate, power and substrate-to-electrode distance on the plasma properties is evaluated, and correlated with the change of PTFE surface energy and surface composition, determined by water contact angle measurements and X-ray photoelectron spectroscopy respectively. [Preview Abstract] |
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CTP.00130: Numerical analysis of fundamental properties in helium dc glow discharges at sub-atmospheric and atmospheric pressure Akinori Oda, Takashi Kimura Fundamental discharge properties in helium dc glow discharges at sub-atmospheric and atmospheric pressure have been simulated using a self-consistent one-dimensional fluid model, which is composed of the continuity equation for electrons, ions, excited atoms and molecules, the Poisson equation, and the energy balance equation for electrons and helium gas. The range of gas pressure is set to be from 50~Torr to 760~Torr in this study. From simulation results, with an increase in gas-pressure up to atmospheric-pressure, dominant positive ion species changes He$^+$ at 50~Torr to He$_2^+$ at the gas-pressure greater than 200~Torr, due to rapid increase in reaction rate of the charge-transfer collision process; ${\rm He}^+ + 2{\rm He} \rightarrow {\rm He}_2^+ + {\rm He}$. The gas-pressure dependence of the spatial profiles in the charged species density, the electric field and the gas temperature will be also discussed at the conference. [Preview Abstract] |
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CTP.00131: Investigations of pulsed dielectric barrier discharge energy efficiency Nicolas Mericam-Bourdet, Micheal J. Kirkpatrick, Emmanuel Odic, Didier Frochot, Frederic Tuvache The use of dielectric barrier discharges (DBD) to generate atmospheric pressure non-thermal plasmas has received a lot of attention recently. The main applications of these discharges are ozone generation and gas effluent cleanup. In all these fields, the energy efficiency of the process is a major concern to attain economically viability. In order to clarify the influence of the power supply, investigations on dielectric barrier discharge were carried out with two types of power supply (pulse, resonance) and two reactor geometries (cylinder-cylinder and pin to pin). A solid-state pulsed high voltage generator with pulse rate rise up to 1 kV/ns and a resonance high voltage power supply with rate rise of 1 kV/ms, were used to compare their ozone generation efficiency when coupled to two different DBD reactors. The first reactor had a cylinder-cylinder geometry and the second had a pin to pin geometry. Ozone generation efficiency will be compared and discussed for the four configurations. [Preview Abstract] |
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CTP.00132: Comparative study of homogeneous dielectric barrier discharge in air and in pure N2 Damien Biran, Nicolas Naud\'e, Nicolas Gherardi Dielectric Barrier Discharges (DBD) is a very simple and robust way to produce non thermal discharges working at atmospheric pressure. It is now well-known that depending on the gas and the electrical parameters, DBD can operate in a homogeneous mode rather than in the more classical filamentary mode. Thus, it is possible to generate an Atmospheric Pressure Townsend Discharge (APTD) in pure nitrogen. In this work, we report that a slight modification of the electrode configuration allows generating a homogeneous discharge in air, staying at atmospheric pressure. The discharge properties of this new discharge in air are studied through electrical measurements, by short time exposure photographs, and by optical emission spectroscopy. The aim is to help in the understanding of the processes which control the obtaining of this homogeneous mode in air. [Preview Abstract] |
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CTP.00133: Electrical characterization of atmospheric plasma sources applied to ancient paper decontamination Mohamed El Shaer, Tarek Abdel Fatah, Mona Mobasher, Michel Wuttmann Different types of atmospheric pressure non-thermal plasma sources are used to treat old paper against fungus and bacterial contaminations. Plasma operated at nearly the ambient temperature, has a great advantage in treating ancient paper due to its dry nature. Comparisons are made between different plasma sources as needle, micro-plasma jet and DBD. Measurements of the plasma electrical parameters of those discharges during the decontamination process help to identify the domain of applications suitable for each type of discharge. Plasma needle is operated in helium at 27.12 MHz, the discharge voltage, current and the power dissipated are measured at the needle in different operating conditions. Micro-plasma jet and DBD are operated at 15 KHz. The variations of the plasma gas temperature measured by an infrared thermometer and the electron temperature measured by a single Langmuir probe against RF perturbation are studied depending on the discharge frequency. The action of different plasma sources are compared through the application of the plasma on a culture of Aspergillus niger, which is a type of fungus commonly found in old papers. [Preview Abstract] |
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CTP.00134: Propagation dynamics of a streamer-like discharge in a He/Ar atmospheric pressure plasma jet Brian Sands, Shih Kang Huang, Jared Speltz, Matthew Niekamp, Biswa Ganguly Using a 20 ns risetime positive unipolar voltage pulse, a streamer-like discharge is generated in a He gas jet with a small Ar admixture that is effused into ambient air from a 2 mm ID glass capillary. The anode is electrically isolated by the glass dielectric barrier resulting in a very stable discharge, which allowed us to acquire spatiotemporally resolved emission from He 3$^3$S$\rightarrow$2$^3$P and 3$^3$D$\rightarrow$2$^3$P to track the propagation of the ionization front up to 50 mm from the tip. The He emission lines appear in time before the emission from both Ar and air molecules and due to their higher excitation threshold energies, they provide a more precise marking of the streamer head. The streamer speed is first accelerated over a few mm distance near the capillary tip, then reaches a quasi-steady propagation speed before decelerating in the outer region of the jet. Addition of Ar to the He flow increases streamer speed by $\sim$20\%, peaking at 1-2\% Ar admixture, corresponding to the minimum in the discharge initiation delay. The dependence of the plasma jet propagation dynamics on both applied voltage and anode location has been measured, and a discussion of the underlying mechanism will be presented. [Preview Abstract] |
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CTP.00135: Evidence for surface streamers self-synchronisation in N$_{2}$/O$_{2}$ mixtures Ilya Marinov, Olivier Guaitella, Antoine Rousseau Surface DBD discharges are widely used for surface treatment, in air purification reactors and as air flow control actuators. Mechanisms involved in streamer/surface interaction are still barely understood, especially for the breakdown phase. This work aims to prove streamer synchronized breakdown. Experimental setup consists of two high voltage electrodes kept at the same potential in contact with a Pyrex disk. iCCD imaging is done through a transparent salted water reservoir used as a grounded electrode. The pictures are collected if only one current peak occurs during the gate time of the camera. Statistical analysis shows the probability of synchronization (PS) i.e. detection of the plasma filaments simultaneously on both electrodes. PS is about 50{\%} in air, 40{\%} with a glass plate placed between the electrodes ($\lambda \quad >$ 300 nm) but PS is equal to zero when black filter is inserted. We propose photodesorbtion of charge deposited by the streamers during previous period to be the plausible synchronization mechanism. Dependence of PS on the oxygen content in the mixture shows an important role of O$_{2}^{-}$. [Preview Abstract] |
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CTP.00136: Influence of energy deposition mode on plasma bullets development Olivier Guaitella, Fran\c{c}ois Pechereau, Anne Bourdon, Antoine Rousseau Plasma bullet obtained mainly in Ar and He are of growing interest especially for biomedical application. The role of capillary tube surface in the bullet sustainment is still not well understood. In this work, the minimum energy density required to start a bullet is studied for different tube diameter, with several type of high voltage sources. The simultaneous measurement of charge deposition and fast imaging gives an insight on the role of charge adsorption for this kind of propagating mechanism. Molecular gases are also investigated with N2/O2 mixture diluted into Ar, especially for exhibiting the role of attachment on O$_{2}$ as a barrier for bullet development. [Preview Abstract] |
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CTP.00137: Spectroscopic Investigations on OH Radicals Generated in He/Water and Air/Water Mixtures by an Atmospheric Pressure Surface Discharge Micro Plasma Device Ken Takiyama, Hideo Nojima, Tsuyoshi Noi, Sinichi Namba, Tsutomu Yamasaki We report the optical spectroscopic study on OH radicals generated by a surface discharge micro plasma device in atmospheric pressure He/water and air/water under the several experimental conditions. Strong emission bands of OH radicals were observed in He/water and the intensity showed the super-linear dependence on the applied voltage. However, the emission was not confirmed in air/water because of the interference by N$_{2}$ emissions. Based on these results, generation and annihilation processes of excited OH radicals in both He/water and air/water mixtures are briefly discussed. [Preview Abstract] |
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CTP.00138: Investigations of Hydrocarbon Contamination in Ozone Generators Jose L. Lopez, Alfred Freilich, Kurt H. Becker, Fabio Krogh Residual amounts of methane (CH$_{4})$ and other trace hydrocarbons in the feed gas of dielectric barrier discharge (DBD) ozone generators have been observed to be a very harmful contaminant in ozone formation. This research aimed to better understand the physical and chemical mechanisms involved in the hydrocarbon contamination of the ozone producing microplasmas. Previous observations of similar hydrocarbons and other trace impurities such as H$_{2}$ or NO$_{x}$ mixed with the feed gas have shown similar degradation effects in ozone formation. Some of these processes caused catalytically enhanced recombination of O atoms, while other impurities lead to different ozone destruction cycles. In this work, both theoretical and experimental methods were used to elucidate the damaging effects of hydrocarbon corruption. [Preview Abstract] |
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CTP.00139: CAPACITIVELY COUPLED PLASMAS |
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CTP.00140: Tuning and biasing techniques for multiple frequency capacitive plasmas in ferromagnetic PVD applications and their effect on film quality Egmont Semmler, Stefan Bienholz, Peter Awakowicz, Tim Baloniak, Achim von Keudell Multiple frequency capacitively coupled plasmas (MFCCP) are a well-known tool for large area etching or PECVD purposes. In contrast, they are rarely used in physical vapour or reactive sputter deposition. However, they provide an interesting alternative for thin film deposition of special systems like ferromagnetic materials. In this work we discuss a dual frequency discharge with excitation frequencies in the VHF and HF band. The influence of various external parameters like applied power ratio and relative phase on plasma properties is studied using a voltage-current probe, a Langmuir probe, phase resolved optical emission spectroscopy (PROES) and a plasma series resonance (PSR) current sensor. These data are compared to simulation results. Deposition experiments with pure iron (Fe) and nickel (Ni) targets using a new arbitrary waveform substrate bias for dedicated ion energy control have been performed. Resulting film properties are correlated to different bias voltage waveforms. Additionally, results are compared to similar findings in reactive deposition of alumina. [Preview Abstract] |
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CTP.00141: Low pressure gas breakdown in longitudinal combined electric fields Valeriy Lisovskiy, Nadiia Kharchenko, Vladimir Yegorenkov This paper contains the complete experimental and analytical picture of gas breakdown in combined electric fields for arbitrary values of rf and dc fields. To obtain it, we continued the study of the discharge ignition modes in nitrogen with simultaneous application of dc and rf electric fields presented in Lisovskiy V. \textit{et al}. 2008 J. Phys. D: Appl. Phys. 41 125207. To this end, we studied the effect of rf voltage on dc discharge ignition. When we applied the rf voltage exceeding one corresponding to the minimum breakdown voltage of a self-sustained rf discharge, then the curve of the dependence of a dc breakdown voltage of a combined discharge on gas pressure was found to consist of two sections. We got the generalized gas breakdown criterion in combined field valid for arbitrary values of rf and dc electric fields. The calculation results agree with experimental data satisfactorily. [Preview Abstract] |
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CTP.00142: Higher harmonic frequencies in capacitive discharges Pavel Dvorak The contribution deals with higher harmonic frequencies that are produced in capacitively coupled discharges due to the nonlinearity of sheaths. Higher harmonics are strong especially at low pressure and they can have a significant influence on plasma. Moreover, they are a tool for plasma diagnostics and monitoring. In this work, dependence of amplitudes of higher harmonics on plasma parameters is studied experimentally. Decrease of pressure causes resonant amplification of harmonics probably related to the series plasma-sheath resonance. Similarly, decrease of electron concentration lead to a resonant amplification. Further, effects of RF power and state of the matching unit were compared. Finally, it was shown that harmonics sensitively react on presence of a deposited film which makes them suitable for monitoring purposes. [Preview Abstract] |
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CTP.00143: Two modes of ccp rf discharge in CF4 Olga Proshina, Tatyana Rakhimova, Alexander Rakhimov, Dmitry Voloshin Ccp rf discharge in CF$_{4}$ has been studied by the use of a 1D PIC MC model. Two different discharge modes are observed depending on discharge conditions: the regime of electronegative plasma with high electron temperature in the bulk and the regime of electropositive plasma with abnormally low electron temperature in the bulk. Characteristic features of two discharge modes are considered. The sharp transition from the former to the last mode is observed with the increase in applied voltage. The dependence of the transition voltage on gas pressure is analyzed. In the studied range of gas pressures the existence of the high temperature mode in CF$_{4}$ is provided by the balance between ionization rate and attachment rate in the bulk region. As a result the transition voltage increases with the gas pressure because of the increased relative role of electron attachment. It is shown that the differences in the used electron cross section sets may noticeably affect the simulation results and discharge properties. Three different electron cross section sets for CF$_{4}$ are considered. In particular, the transition voltage between two discharge modes differs essentially for different cross sections used. [Preview Abstract] |
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CTP.00144: Excitation dynamics in electrically asymmetric capacitively coupled radio frequency discharges Julian Schulze, Zoltan Donko, Edmund Schuengel, Uwe Czarnetzki The symmetry of capacitively coupled radio frequency discharges can be controlled electrically by applying a fundamental frequency and its second harmonic with adjustable phase shift $\theta $ between the driving voltages to one electrode. A variable DC self bias $\eta $ is generated as a function of $\theta $ via the Electrical Asymmetry Effect. Here excitation dynamics in electrically asymmetric geom. symmetric dual frequency discharges operated in argon at 13.56 + 27.12 MHz is investigated experimentally, by a PIC simulation, and by an analytical model. At low pressures (collisionless sheaths) the excitation dynamics works similar to classical discharges: The maxima of the time modulated excitation at the powered and grounded electrode within one low frequency period will be different (asymmetric excitation), if $\eta $ is strong at $\theta \approx $0\r{ } 90\r{ } and similar (symmetric excitation), if $\eta \approx $0 V at $\theta \approx $45\r{ }. At high pressures (collisional sheaths) the excitation dynamics is found to work differently. The excitation will be symmetric, if $\eta $ is strong, and asymmetric, if $\eta \approx $0 V. These phenomena are understood by an analytical model. [Preview Abstract] |
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CTP.00145: Simulation study of collisionless heating in capacitively coupled discharges Sarveshwar Sharma, Miles M. Turner Collisionless heating is important in low-pressure radio-frequency discharges, such as capacitive discharges. Recent theoretical work on this problem using several different approaches has produced results that are broadly in agreement insofar as scaling with the discharge parameters is concerned, but there remains some disagreement in detail concerning the absolute size of the effect. In this paper we report a simulation study that has two main aims. One is to investigate the limitations of the scaling law, especially in the case of high frequency where resonant circuit effects occur, and where plasma wave emission may be observed at the sheath edge in simulations. The second aim is to produce a relatively extensive set of simulation data that may be used to validate theories over a wide range of parameters. [Preview Abstract] |
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CTP.00146: Multiple frequency capacitive plasmas for PVD: Influence of external process parameters on ferromagnetic film properties Stefan Bienholz, Egmont Semmler, Peter Awakowicz, Hayo Brunken, Alfred Ludwig Over several years capacitively coupled plasmas have been of great importance in PVD coating processes. Sputtering ferromagnetic targets, typical magnetron coaters need rather complex magnetic configuration to sustain a reasonable deposition rate. To overcome such problems, we propose a multiple frequency driven capacitively coupled plasma (MFCCP). Whereas plasma excitation in the VHF and HF band cause a high ion flux with large bombarding energies on the target electrode, an additional substrate bias is used to control the ion energy directly on the substrate surface to influence the morphology and crystallinity. In this contribution we discuss the result from different coating experiments using pure iron (Fe) and nickel (Ni) targets. General film properties such as thickness, morphology, and crystalline composition are investigated as well as magnetic properties. The experiments document an suitable control of film properties and show that MFCCPs are a promising complement to existing ferromagnetic sputter processes. [Preview Abstract] |
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CTP.00147: Deposition mechanism of hydrogenated carbon films by rf (13.56MHz) CH$_{4}$ plasma Mohamed Ouchabane, Houria Salah, Mohamed Kechouane Plasma enhanced chemical vapour deposition technique (PECVD) was used to grow diamond-like carbon films. The used deposition system is magnetically confined chamber with parallel electrodes. The results showed that the structure depends strongly on the applied bias voltage. In the range of energy considered the growth of the films was governed by a competition between both chemical and physical processes, with a dominance of physical process (subplantation) above 240 V, the energy at which more than 90{\%} sp$^{3}$ hybridization was obtained. [Preview Abstract] |
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CTP.00148: The EAE in geometrically asymmetric dual frequency capacitively coupled radio frequency discharges Edmund Schuengel, Julian Schulze, Uwe Czarnetzki Capacitively coupled radio frequency (CCRF) discharges are widely used for surface processing applications. Geometrically asymmetric CCRF discharges typically consist of a powered electrode with surface size A$_{p}$ placed in a grounded vacuum chamber with wall surface area A$_{g} \quad >>$ A$_{p}$. In order to compensate the flux of electrons and positive ions at each electrode within one rf period, a DC self bias $\eta $ develops. High ion energies at the powered electrode surface lead to unique processing opportunities. The Electrical Asymmetry Effect (EAE) is based on the application of a fundamental frequency and its second harmonic with an adjustable phase $\theta $ to the discharge. It allows the control of $\eta $ and the ion energies in a geom. symmetric discharge. Here, the DC self bias and the ion energies are measured in a geom. and electrically asymmetric discharge. The geom. asymmetry shifts the control range of $\eta $ to smaller values. Depending on the particular choice of $\theta $, the ion energy is increased at the powered electrode or at the grounded surfaces promising better chamber cleaning conditions. The results are understood by means of an analytical model. Funded by the Ruhr-University Research Department Plasma and the A. von Humboldt Foundation. [Preview Abstract] |
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CTP.00149: Power dissipation in electrically asymmetric dual frequency capacitively coupled radio frequency discharges Edmund Schuengel, Julian Schulze, Zoltan Donko, Uwe Czarnetzki For many applications of capacitively coupled radio frequency discharges, separate control of ion energy and ion flux towards a processed surface is of paramount importance. This separate control is not possible in single frequency discharges and is limited in classical dual frequency discharges operated at substantially different frequencies due to the frequency coupling. Using the new concept of the Electrical Asymmetry Effect a fundamental frequency and its second harmonic are applied to the powered electrode of a geometrically symmetric discharge. The ion energy is controlled via the phase angle $\theta $ between the frequencies, while the ion flux remains almost constant. The independence of the flux on $\theta $ is the result of the power dissipation investigated experimentally and by means of a PIC simulation. An analytical model shows why the ion flux is constant at high pressures as well as at low pressures, where the plasma series resonance is self-excited leading to additional electron heating. Funded by the Ruhr-University Research Department Plasma, the A. von Humboldt Foundation, and the Hungarian Fund for Scientific Research (OTKA K77653). [Preview Abstract] |
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CTP.00150: Experimental and theoretical study of dynamic effects in low-frequency capacitively coupled discharges Dmitry Voloshin, Oleg Braginsky, Alexander Kovalev, Dmitry Lopaev, Olga Proshina, Tatyana Rakhimova, Anna Vasilieva Investigation of the low frequency capacitive coupled RF discharge in Ar excited at 1.76 MHz is performed both experimentally and theoretically. Experimental measurements of electron concentration, discharge voltage and current are presented for a wide range of input power. The experimental current shape has non-sinusoidal, close to triangle form. Theoretical study is based on the Particle in cell with Monte-Carlo Collisions numerical simulation. The triangle shape of the discharge current is obtained even for the case of a symmetric discharge. This is caused by the dynamic structure of the discharge sheaths. The sheath edge motion is non-sinusoidal and non-symmetric. Other specific dynamic features of low-frequency discharge are discussed. The important role of secondary electrons in discharge maintenance and power balance is described. This study is crucial for further treatment of dual frequency discharges with corresponding low frequency value. [Preview Abstract] |
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CTP.00151: Capacitively coupled radio-frequency discharges in nitrogen at low-pressure L.L. Alves, L. Marques, C.D. Pintassilgo, G. Wattieaux, J. Berndt, L. Boufendi, G. Cernogora This paper uses simulations and measurements to study capacitively coupled rf discharges (13.56 MHz) in pure nitrogen, produced within a cylindrical parallel-plate reactor, at 0.2-2 mbar pressures and 20 -30 W coupled powers. The reactor is similar to a GEC reference cell surrounded by a lateral grounded grid. Simulations use an hybrid code that couples a 2D ($r$,$z)$ time-dependent fluid module, describing the dynamics of charged particles, and a 0D kinetic module, describing the production and destruction of nitrogen (atomic and molecular) neutral species. The coupling between these modules adopts the local mean energy approximation to define space-time dependent electron parameters for the fluid code and to work-out space-time average rates for the kinetic code. Model results are compared to measurements of the self-bias potential, the effective rf power (accounting for circuit losses), the average electron density (obtained by resonant-cavity measurements), and the intensities of radiative transitions with the nitrogen SPS and with atomic lines emitted by argon traces (obtained by OES diagnostics). [Preview Abstract] |
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CTP.00152: Characterization of a low pressure capacitively coupled RF discharge in N2-H2 G. Wattieaux, J. Berndt, E. Kovacevic, M. Mikikian, L. Boufendi, N. Carrasco, G. Cernogora, A. Gouveia, C.D. Pintassilgo, L. Marques, L.L. Alves Discharges operated in mixtures of hydrogen and nitrogen are nowadays used as a source of active species for various kinds of applications from etching of low-k materials to modifications of polymer surfaces for biomedical applications. Moreover these kinds of discharges can provide information relevant for studies of planetary atmospheres. The present work involves the study of a low pressure capacitively coupled RF discharge operated in variable mixtures of N2 and H2 at variable pressures and powers. The systematic measurements of electron density, RF voltage, self bias and the observation of several molecular bands by means of optical emission spectroscopy gave us important information about basic processes relevant for the understanding and application of such kind of discharges. The experimental results are interpreted by means of a hybrid model, namely the effect of admixing hydrogen into a N2 discharge. [Preview Abstract] |
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CTP.00153: Characteristics of electron heating and confinement and their changes by means of phase delay in push-pull concept CCP source Myung-Sun Choi, Seok-Hwan Lee, Gon-Ho Kim, Doungyong Sung Individual control of ion energy and flux and their species is most desired technique in plasma processing for modern dry etching technology. The ion flux is proportional to the plasma density which can be controlled by applied RF power. The ion energy is proportional to the sheath potential which depends on the amplitude of RF voltage on the electrode. The dissociation rates of gas species are closely related with the electron energy distribution. Dual frequency capacitively coupled plasma (CCP) sources are typically used to control ion bombardment energy and ion flux individually, but it cannot control the electron energy distribution independently. The push-pull concept of CCP source were developed for individual electron energy distribution control which applied very high frequency RF power on top and bottom electrodes with some phase delay. In the push-pull powered source, since the electrical response of plasma is distorted due to the phase delay of power between the top and bottom electrode, electron energy distribution function is modified by means of balance between heating and confinement. This work investigates the changes of heating and confinement and their mechanism by means of phase delay in the push-pull dual frequency capacitively coupled plasma source. [Preview Abstract] |
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CTP.00154: Langmuir wave standing wave resonance in DC/RF plasma Lee Chen, Merritt Funk The electron energy distribution function (EED$f)$ of parallel-plate plasma
with a high-negative DC electrode and an opposing RF electrode is far from
Maxwellian [L. Chen \textit{et} \textit{al}., Proc. on 31$^{st}$ Dry Processing Symposium, 1--3
(2009) 7]. It has four distinct energy-groups, in descending order:
DC-cathode injected ballistic electrons (BE), continuum, middle-energy peak,
Maxwellian. The middle-energy peak has energy ($E_{M})$ in the range of $\sim
$ 40eV$ |
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CTP.00155: MICRODISCHARGES: DC., RF, MICROWAVE |
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CTP.00156: The effect of nitrogen impurity on the DC breakdown voltage in argon at micrometer gaps Matej Klas, Stefan Matejcik, Marija Radmilovic-Radjenovic, Branislav Radjenovic The dc breakdown voltage has been investigated experimentally in a discharge system consisting of two parallel planar Cu electrodes at separation of 100 $\mu $m, focusing on addition of a small amount of nitrogen to argon gas. The recorded breakdown voltage curves show the well-known V-shaped characteristics. It was found that the breakdown potential increases with increasing nitrogen concentrations especially at the right hand side of the breakdown voltage curves. The experimental data are compared with the PIC/MCC simulation results and a satisfactorily agreement has been achieved. [Preview Abstract] |
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CTP.00157: Self-consistent modeling of atmospheric micro-plasmas produced by a microwave source L.L. Alves, J. Greg\'orio, P. Leprince, C. Boisse-Laporte This paper presents the self-consistent modeling of argon micro-plasmas, produced by a microwave source (2.45 GHz) at atmospheric pressure [1]. Simulations use a 1D, stationary hybrid code that solves the fluid-type transport equations for electrons, positive ions Ar$^{+}$ and Ar$_{2}^{+}$, and the electron mean energy; the rate balance equations for the main neutral species; Poisson's equation for the space-charge electrostatic field; Maxwell's equations for the electromagnetic excitation field; the gas energy balance equation for its temperature distribution; and the kinetic electron Boltzmann equation considering several direct and stepwise electron collisions processes. The model uses a kinetic scheme that considers the atomic excited states Ar(4s) and Ar(4p), two excimer states Ar$_{2}$* and Ar$_{2}$**, and two ionization states associated to the atomic and the molecular ions. The model predicts power densities of 1-5 kW cm$^{-3}$ and gas temperatures of 400-700 K, for electron densities of $\sim $10$^{13}$-10$^{14}$ cm$^{-3}$, in agreement with measurements. Simulations exhibit a strong dependence on the gap-size and the electron density. [1] J. Greg\'{o}rio et al, these proceedings. [Preview Abstract] |
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CTP.00158: Microplasmas for Clinical Breath Analysis Paul Maguire, James Greenan, Charles Mahony, James McLaughlin, Davide Mariotti Breath analysis is receiving increased attention for clinical diagnosis and microplasmas may offer scope as a lab-on-chip sensor for point of care diagnostics. However metabolite detection and recognition is an extremely challenging problem and will require robust high intensity sources and advanced signal analysis. Using parallel-plate devices and neural nets we previously established distinguishability for various stages of asthma [1, 2]. We present recent systematic analysis of gas detection capability using high intensity RF and DC sources. Data was obtained from optical (visible) emission spectra, infra-red emission spectra (NIR - MIR) and from VI spectra in various current modes at atmospheric or low pressure ($<$50T) conditions. A number of data analysis techniques were studied in order to determine the most suitable strategies for pattern recognition.\\[4pt] [1] Hyland, M. et al., Applications {\&} Science of Neural Networks, Fuzzy Systems, and Evolutionary Computation (III) \textbf{4120} (2000) 246-252\\[0pt] [2] Mariotti D et. al., Plasma Sources Sci. Technol. \textbf{13 }(2004) 207--212. [Preview Abstract] |
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CTP.00159: RF Micro-Hollow Device Sustainment, Ignition and Mode Transitions C.M.O. Mahony, J. Greenan, P. Maguire Rf Micro-Hollow Devices (rfMHD) are new micro-plasma sources which provide plasmas from the millimetre scale to below 10 microns. These sources ignite readily and operate stably at powers less than 10W at near atmospheric pressure. Several discharge modes are evident, providing novel ignition and steady state physics. The devices are aimed at applications such as targeted processing of human cells and other bio-materials, processing of inorganics, sensors and light sources. The electrical and optical characterisation of a number of discharge configurations over a range of control parameter values will be presented. Effective electron temperature is derived from OES via a collisional radiative model, VI characteristics in various discharge modes are used to examine sustainment processes and mode transition/ignition. The results of scaling studies will be used to investigate the limits of RfMHD operation and provide comparison with standard dc operated sources. [Preview Abstract] |
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CTP.00160: Optical Emission Study of a Direct-Current, Atmospheric-Pressure Non-Thermal Plasma Microjet WeiDong Zhu, Jose L. Lopez, Kurt H. Becker This work aims to study a direct-current driven, atmospheric-pressure non-thermal plasma microjet (PMJ) operated in air with mixtures of He or He/O$_{2}$ as the working gases with a typical current of 5-40 mA and a gas flow rate of 2-5 slm. Optical emission spectra were taken from end-on and in some cases from side-on (at different distances from the exit nozzle). End-on spectra show major He emission lines as well as weak emissions the N$_{2}$ 2$^{nd}$ positive system (C$^{3}\Pi _{u}$-B$^{3}\Pi _{g})$. Strong atomic oxygen emission was also observed. Similar emissions were observed when the He/O$_{2}$ PMJ was submerged in water. The strong emission of oxygen can result from direct He* penning ionization of O$_{2}$ molecules followed by the electron-impact dissociation of O$_{2}^{+}$. The relative intensity of the oxygen was found to increase with the increase of the operating current and peaked at an O$_{2}$ volume concentration of 0.1{\%}-0.3{\%}. [Preview Abstract] |
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CTP.00161: Investigation of the Capillary Plasma Electrode (CPE) Discharge Jose L. Lopez, Valencia Johnson, WeiDong Zhu, Kurt H. Becker The Capillary Plasma Electrode (CPE) discharge is able to produce stable atmospheric pressure nonequilibrium plasmas. The CPE discharge is essentially a barrier-electrode discharge with perforated dielectrics. Discharge from this configuration, aside from exhibiting a diffuse mode of operation, also exhibits a distinct mode namely, ``the capillary jet.'' As the frequency of the source is increased above a few kilohertz, one first observes the diffuse mode, but a certain frequency is then reached at which the capillaries ``turn on'' and bright plasma jets are observed to emerge from the capillaries. The distinction between the diffuse and capillary modes is dramatic. The capillary jets seem to overlap so that the discharge appears uniform when the electrode contains an array of capillaries. This current work explores these modes of operation by characterizing the electrical and optical emission properties of this discharge by correlating a multi-capillary discharge and a single capillary discharge reactor. [Preview Abstract] |
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CTP.00162: Simulation of partial discharges in voids in insulating materials Reidar Svein Sigmond, Alice Goldman, Max Goldman Partial discharge literature reports that in new voids, the current pulses generated by partial discharges have short rise times, last only a few nanoseconds and generally have a great amplitude. After a given ageing, when the walls are oxidized, the current pulses have a longer rise time, a longer duration and a lower amplitude. The paper presents results obtained for the current pulses by a computer simulation of the equivalent electrical circuit of the whole system (comprising a pulsed power supply, the void and its surrounding dielectric) with ``reasonable'' ionization coefficients for the development of the partial discharges. Special attention is paid to the role of the void size in the discharge development. [Preview Abstract] |
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CTP.00163: Ageing processes of the voids in insulating materials Max Goldman, Alice Goldman, Reidar Svein Sigmond It is generally agreed that the partial discharges which occur in the voids in insulating materials can be considered as a sign of the beginning of ageing of the bulk material. The gas and surface of electrically stressed voids are not static, but change continuously with time from the first discharge onwards. While one might assume that the first discharge pulses occur in air at atmospheric pressure, the oxygen will rapidly be consumed, the pressure will fall and reactive products will be formed. Acid products will appear on the void surface and react with it. These changes will be reflected in the shape, size and frequency of the observable partial discharge pulses. Properly interpreted, these may serve as useful indicators of the state of the insulating materials. [Preview Abstract] |
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CTP.00164: Simulation studies of Micro Cavity Discharges for Microthruster Applications Hariswaran Sitaraman, Laxminarayan. L. Raja Direct-current (DC) microdischarges have been proposed for several applications such as in photonics and materials/chemical processing. They are well suited for integration within micro propulsion devices for small satellite thrusters. However, one important limitation in these devices is the rapid erosion of exposed electrodes due to sputtering and ion bombardment heating. An alternative approach is to use dielectric-covered electrodes with alternating current to drive the discharge. The Micro Cavity Discharge (MCD) thruster adopts this approach and consists of a channel section with dielectric covered electrodes where the plasma power deposition takes place and a divergent nozzle through which the gas expands to near vacuum conditions in space. The system now resembles a Micrometer scale Dielectric-Barrier Discharge (Micro DBD) which operates in a pulsed mode and is accompanied with high gas heating. Multi-dimensional computational plasma and flow modeling studies of these devices are presented. We present details of discharge dynamics, power coupling mechanisms, flow-plasma coupling effects and thruster performance. Results indicate that large gas heating is possible with high-frequency $\sim $10's MHz, rather than the typical excitation frequency of $\sim $ kHz used in classical DBDs. [Preview Abstract] |
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CTP.00165: The effects of dielectric layer and a driving method on the discharge characteristics of atmospheric-pressure micro plasmas Hyo-Won Bae, Jong-Bong Lee, Ho-Jun Lee, Hae June Lee Atmospheric pressure plasmas which do not need a vacuum chamber have attracted great attentions for various applications such as surface modification and bio medical equipment. A one-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) simulation is adopted to understand the characteristics of a parallel-plate micro plasma with a driving frequency varying from 13.56 MHz to 100 MHz and with a gap distance less than 100 micrometers. The difference between a dielectric barrier discharge and a dielectric-free discharge is investigated by comparing the spatiotemporal evolution of plasma density and excitation collisions as well as the electron energy distribution function (EEDF). Also, investigated are the effects of driving method such as sinusoidal RF and pulsed-DC on the EEDF and excitation collisions. With the choice of driving method combined the choice of whether dielectric barriers exist or not, it is possible to select a preferable EEDF of a micro atmospheric pressure plasma. [Preview Abstract] |
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CTP.00166: Anomalous response of lossy plasmas immersed in metamaterial structure in the microwave range Osamu Sakai, Takuya Shimomura Microwave response of a plasma metamaterial which is a periodic array composed of lossy microplasmas and magnetic micro resonators was investigated experimentally. We generated microplasmas whose real part of permittivity was negative with significantly large imaginary part, and in their vicinity magnetic resonators were installed which showed complex-value macroscopic permeability. When microwaves at several GHz were transmitted through this metamaterial, signals from the receiver in the cases of plasma generation decreased and sometimes \textit{increased}, which depends on the discharge gas condition that leads to change of imaginary part of permittivity. In particular, enhanced transmission of microwaves when lossy plasmas were generated would be an anomalous response if metamaterial functions were not effective. [Preview Abstract] |
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CTP.00167: Phase Resolved OES of Coaxial Microplasma Jet Operated in He or Ar Jan Benedikt, Sven Hofmann, Nikolas Knake, Henrik B\"{o}ttner, R\"{u}diger Reuter, Achim von Keudell, Volker Schulz-von der Gathen The study of excitation mechanism of a coaxial microplasma jet with a hollow capillary as an inner electrode and a ceramic tube surrounded by a metal ring as the outer electrode. The jet is operated in He and Ar gas and electrical measurements, optical emission spectroscopy and space and phase resolved wavelength integrated optical spectroscopy are use for ist analysis. Four different modes are distinguished with He as plasma forming gas. The $\alpha$ discharge in annular space between the electrodes, observed at low applied voltages, is very similar to the discharge in jets with parallel electrodes. As the voltage increases a $\gamma$ discharge appears, first localized at the tipp of the capillary. As the voltage increases further the $\gamma$ discharge appears in the annular space as well. A hollow cathode plasma is observed at any voltage used on the symmetry axis of the jet. Only one mode of plasma operation is observed in argon gas with distinctively different behavior. We hypothesize that it is comparable to a single microdischarge of a filamentary dielectric barrier discharge. [Preview Abstract] |
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CTP.00168: Micro-Discharges within Voids of Sub-Millimeter Dimensions Alireza Ganjovi, Ghasem Rastpoor A two-dimensional kinetic model to study the evolution of micro-discharges within a void of sub-millimeter dimensions inside polymeric dielectrics has been developed using a Particle-in-Cell (PIC) algorithm. The formation of avalanches in gas-filled channels by ionization and electron attachment is traced. The elastic and inelastic inter-particle collisions are simulated using a stochastic Monte Carlo Collision (MCC) technique. The Poisson's equation is solved using the dynamic alternating direction implicit (DADI), which has good convergence. The discharge within the void is studied in conjunction with the external circuit. Secondary processes including photo-emission and ion-emission from the cathode are considered. The model studies the development of avalanche discharges within channels and the role of the space charge modified field during propagation of micro-discharges. The model is used to successfully simulate the evolution of the discharge and yield useful information about the build-up of space charge within the channel and the consequent modification of the applied electric field. The effect of width of void on the number of micro-discharges and their propagation will be studied. [Preview Abstract] |
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CTP.00169: Dynamics of atmospheric pressure plasma bullets in He-Ar mixtures Julien Jarrige, Erdinc Karakas, Mounir Laroussi Atmospheric pressure non-thermal plasma jets in ambient air have received great attention for their potential in biomedical applications. Several studies have shown that NTP jets are not continuous, but composed of plasma bullets traveling at high velocities. In this work, we present an experimental study of plasma bullets produced in Ar-He mixtures. The plasma jet is initiated in a DBD capillary reactor driven by microseconds high voltage pulses. The effects of argon content on the discharge characteristics, on the bullet propagation, and on the radiative properties of the jet are investigated using electrical measurements, fast ICCD camera imaging, and time-resolved optical emission spectroscopy. It is shown that the propagation velocity of plasma bullets in open air increases with argon content. The addition of a few percent of Ar in the feed gas leads to a significant increase of the emission intensity of N$_{2}$ (C-B) and of highly reactive OH radicals, while N$_{2}^{+}$ (B-X) bands and He lines almost disappear from the emission spectra. The role of He and Ar metastables in the plasma kinetics is discussed. [Preview Abstract] |
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CTP.00170: Time dependence measurement of electron density and temperature of a 60 Hz nonequilibrium atmospheric pressure plasma by laser Thomson scattering Fengdong Jia, Naoya Sumi, Kenji Ishikawa, Hiroyuki Kano, Hirotoshi Inui, Keigo Takeda, Hiroki Kondo, Makoto Sekine, Masaru Hori A nonequilibrium atmospheric pressure plasma excited by 60 Hz ac power was diagnosed by laser Thomson scattering. We studied the electron temperature ($T_{e})$ and density ($n_{e})$ in one ac cycle. The results showed that the plasma generated in a frequency of 120Hz, and occupied half of every half ac cycle with about 1ms delay shift compared with ac voltage waveform. During the discharge periods the $T_{e}$ was almost same about 1.5eV, and $n_{e}$ reached its maximum around peak value of ac voltage, after that decreased with the decreasing of ac voltage, which changes from about 5.0$\times $10$^{14}$cm$^{-3}$ to 2.0$\times $10$^{14}$cm$^{-3}$. [Preview Abstract] |
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CTP.00171: Quantitative shadowgraphy on an atmospheric DC laminar argon plasma jet Charles de Izarra, Nuno Cerqueira, Gr\'egoire de Izarra The work proposed deals with the diagnostics of a DC laminar argon plasma jet operating at atmospheric pressure in ambiant air using three techniques. Through the pumping effect of ambiant air by the laminar jet, it is possible to observe the UV OH spectrum at 306.357 nm and to perform emission spectroscopy in order to carry out the OH rotational temperature close to the thermodynamic temperature of the gas. In addition, measurements of the refractive index is made by considering two different methods: optical interferometry and quantitative shadowgraphy. It is showed that the temperature obtained by the three diagnostics techniques are very close. [Preview Abstract] |
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CTP.00172: Gas flow dependence of ground state atomic oxygen in plasma needle discharge at atmospheric pressure Nikolas Knake, Yukinori Sakiyama, Daniel Schroeder, David Graves, Volker Schulz-von der Gathen We present measurements of two distinct atomic oxygen density patterns occurring close to an insulating surface in front of the plasma needle discharge at atmospheric pressure according to two different feed gas velocities. These atomic oxygen patterns are correlated to the distinct killing patterns of bacteria which previously have been reported for the plasma needle in literature. Two-photon absorption laser-induced fluorescence (TALIF) spectroscopy in combination with gas flow simulation was employed to obtain spatially resolved absolute density distributions. When the feed gas flow rate is low, atomic oxygen density peaks on the center. At the higher flow rate, atomic oxygen forms a ring-shaped density distribution. The peak density is in the order of $10^{21}$ $m^{-3}$ in both cases. [Preview Abstract] |
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CTP.00173: Plasma dynamics and development of plasma pulses in a kHz generated atmospheric pressure plasma jet Qais Algwari, Deborah O'Connell A cold plasma jet is ignited inside a glass capillary tube and sustained at atmospheric pressure. Two circular electrodes powered with 20 kHz excitation (approx. 6kV) surround the glass tube flowing helium gas. An intense plasma forms inside the glass tube between the two electrodes and a significant plasma plume emerges at either end of the glass capillary. The plasma plume though continuous to the naked eye, when observed on a nano-second time scale consists of discrete plasma pulses moving at a velocity much greater than the discharge gas velocity. We investigate the discharge formation mechanisms and the dynamics of the generated plasma pulses using time resolved optical emission spectroscopy with 3-d spatial resolution. Spectral resolution is also achieved using different interference filters. Different plasma species can be identified to exhibit different spatial profiles -- both axially and radially. Penning ionization of metastable helium with nitrogen molecules is indentified as playing an important role in plasma sustainment. [Preview Abstract] |
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CTP.00174: PLASMA DEPOSITION |
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CTP.00175: Chemical activity of oxygen atoms in the growth of sputter-deposited ZnO films Hajime Shirai, Aya Morita The role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films was studied by alternating the deposition of a several-nanometer-thick ZnO layer and the O$_{2}$/Ar mixture plasma exposure, i.e., \textit{layer-by-layer }(LbL) technique. The film crystallization promoted with suppressing the oxygen vacancy and interstitial defects by adjusting the exposure condition of O$_{2}$/Ar plasma. These findings suggest that the chemical potential of oxygen atom determine the film crystallization as well as the electronic state. The diffusion and effusion of oxygen atoms at the growing surface play a role of thermal annealing, promoted the film crystallization as well as the creation and the annihilation of oxygen and zinc related defects. The role of oxygen atoms reaching at the film-growing surface is discussed in term of \textit{chemical annealing}. The possible oxygen diffusion mechanism is proposed. [Preview Abstract] |
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CTP.00176: Control of Gas Phase and Surface Processes in Plasma Polymerization Dirk Hegemann Plasma polymerization covers several interesting fields from highly functional plasma polymers to hard coatings. While the film growth for hard coatings are mainly determined by ion bombardment yielding densification, rather mild plasma conditions are typically used for the retention of functional groups within less crosslinked plasma polymers. Certain applications, however, require functional plasma polymers showing a high stability. Hence, both the gas phase and the surface processes have to be controlled during the plasma polymerization process. We could demonstrate that the energy invested per particle within the plasma (activation of the chemical reaction pathway) as well as the energy dissipated during film growth (crosslinking) can be used as reaction parameters. While the former scales with power input per unit of gas flow W/F, the latter is governed by the energy density, i.e. ion flux times ion energy per deposition rate, enabling the control by macroscopic parameters. Siloxane (HMDSO) as well as hydrocarbon-based plasmas (CO$_{2}$/C$_{2}$H$_{4})$ were used to optimize the functionality of hydrophobic and hydrophilic plasma polymers revealing that plasma chemical gas phase processes should prevail over surface processes, since strong ion bombardment yields a loss in functionality. [Preview Abstract] |
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CTP.00177: Radiofrequency plasma deposition from Ar/HMDSO/O$_{2}$ glow discharge: Correlation between chemical structure and thin film mechanical and thermal behavior Arup Jyoti Choudhury, Joyanti Chutia, Dinkar S. Patil Hexamethyldisiloxane (HMDSO) films are deposited on bell metal by radiofrequency (RF) plasma polymerization process, using Ar/HMDSO/O$_{2}$ glow discharge. The chemical structure of the HMDSO films is studied by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It is observed that HMDSO films with least defective chemical structure and highest inorganic character exhibits excellent mechanical and thermal behavior. From scratch and nanoindentation test, it is observed that maximum critical load (14.5 mN) is applied on the HMDSO film prepared at RF power of 100 W, which also shows highest hardness (3.9 GPa) and elastic modulus (48.1 GPa). The thermogravimetric analyses (TGA) reveal that degradation temperature of the HMDSO films increases while their percentage of weight loss decreases at higher RF powers. Attempts are made to correlate the chemical structure with the mechanical and thermal behavior of the deposited HMDSO films. [Preview Abstract] |
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CTP.00178: Research on optimum condition to prepare carbon nano structure using MOCVD Takeru Kanazawa, Hiroharu Kawasaki, Tamiko Ohshima, Yoshihito Yagyu, Yoshiaki Suda Carbon nanotubes (CNTs) are promising new materials for a variety of potential applications because of their excellent electrical, mechanical and chemical characteristics. Therefore, CNTs have been produced by various methods such as arc discharge, in a buffer gas, laser ablation, chemical vapor deposition and annealing of nanodiamonds. Recently, CNT-based gas sensors have received considerable attention because of their outstanding properties, such as faster response, higher sensitivity, lower operating temperature and wider variety of gases that may be detected compared with the other types of gas sensors. In this study, we have been prepared CNTs on the Si substrate with metal nanodots on using chemical vapor deposition method. CNTs and nanosize dot structural metal substrates can be prepared on the silicon by using one process in the same chamber. Size of the nanosize dot structural metal on the silicon was about 50$\sim $500 nm and dispersion of them is small. Size and density can be controlled by the substrate temperature and mixture ratio of solution. CNTs on the substrate were several hundred in diameter, and density of them can be controlled by substrate temperature and methane gas pressure. [Preview Abstract] |
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CTP.00179: Structural investigation of hydrogenated amorphous Carbon thin films deposited by PECVD Seyed Iman Hosseini, Babak Shokri, Marzieh Abbasi Firouzjah, Saeed Koushki, Mehdi Sharifian Hydrogenated amorphous Carbon thin films were deposited on Glass and Silicon substrates by low pressure and temperature radio frequency and microwave plasma enhanced chemical vapor deposition. Different mixtures of Methane and Hydrogen were used for deposition of the films. The influences of feed gases ratio and power of generators on the composition, roughness and thickness of the deposited films were investigated. The Raman G peak position shifts toward lower wave numbers for glass substrates by increasing the gas ratio (hydrogen to methane) but has less effect on Si substrate. For Si substrates this shift occurs by increasing the power of generator. [Preview Abstract] |
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CTP.00180: The effect of TEOS/O2 pressure ratio on the silicon oxide films deposited by PECVD Marzieh Abbasi Firouzjah, Seyed Iman Hosseini, Babak Shokri, Mahdi Shariat The effects of the silicon precursor to the oxygen pressure ratio on the properties of silicon dioxide thin films were studied. The films were deposited by organometallic based plasma enhanced chemical vapor deposition method at low temperature. The organometallic tetraethoxy-silane was used as silicon precursor and oxygen was used as oxidant gas. The effects of the R (0.05--1.5) on the film characteristics such as structure and chemical composition, surface topography were evaluated by FTIR and AFM analysis. In addition, mechanisms of deposition phenomenon have been studied as related to the process parameters by using the optical emission spectroscopy and measurement of the film deposition rate. [Preview Abstract] |
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CTP.00181: Characterization of an electron beam generated in the pulsed plasma deposition gun Dmitry Yarmolich, Peter Nozar, Carlo Taliani, Svetlana Gleizer, Yakov Krasik The channel spark discharge was used as a high-current density (up to 30 kA/cm$^{2})$ relatively low energy ($<$20 keV) electron source in a pulsed plasma deposition (PPD) gun. Due to a high energy density deposition, the PPD gun can be applied for the deposition of thin films by pulsed ablation of different target materials, at a background gas pressure in the range 10$^{-2} - 10^{-4}$ Torr. Parameters of the electron beam generated in a modified PPD gun were studied using electrical, optical, and x-ray diagnostics. It was found that the plasma formation between the gun output and target that restricts the energy delivering to the electron beam. It was shown that efficient (up to $\sim $74{\%}) transfer of the initially stored energy to the energetic electron beam is realized at the background gas pressure of 10$^{-4}$ Torr. Conversely, at a pressure of 10$^{-3}$ Torr, only $\le $10{\%} of the stored energy are acquired by the energetic electrons. It was shown that the modified PPD gun, due to extremely high energy density at the target delivered by the electrons, may be applied for the deposition of different materials. The deposition rates and properties of the deposited films (DLC, ZnO, TiO2, W, CdTe, CdS) are discussed as well. [Preview Abstract] |
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CTP.00182: Deposition of fluorinated diamond-like carbon films using pulsed plasma thruster Takashi Kimura, Masayasu Iida Fluorinated diamond-like carbon films are deposited on the silicon substrate by the exposure of the pulsed plasmas where the feed gas is mainly generated from the ablation of insulator. An electrothermal pulsed plasma thruster with a discharge room in an insulator rod is used as the pulsed plasma for ablation of insulator (PPA), and the material of the insulator rod is polytetrafluoroethylene (PTFE). The PPA has an anode at the end of the room and a cathode of divergent nozzle at the exit of the room. Both the anode and the cathode are made of aluminum. The distance of 13 mm between the anode and the cathode is equal to the plasma length. The diameter of the insulator rod is 4 mm. The pulsed plasma is generated by the stored energy in the capacitor connected to the electrodes. The thickness of the fluorinated diamond-like carbon films deposited on the silicon substrate is about 2$\mu$m - 3$\mu$m, and the deposition rate, which depends on the stored energy, is about 0.12-0.20 nm/shot. The hardness of the film, which is measured by nanoindenter, decreases with the increase in the stored energy in the capacitor. The maximum of the hardness is about 5-7 GPa at the stored energy of 2.5-2.7 J. [Preview Abstract] |
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CTP.00183: Room-Temperature Deposition of Silicon Nitride Films with Very High Rates Using Atmospheric-Pressure Plasma Chemical Vapor Deposition Hiroaki Kakiuchi, Hiromasa Ohmi, Kiyoshi Yasutake We have investigated the structure and stability of SiN$_{x}$ films deposited with very high rates ($>$50 nm/s) in atmospheric-pressure (AP) He-based plasma excited by a 150 MHz very high-frequency (VHF) power using a cylindrical rotary electrode at room temperature. The SiN$_{x}$ films are prepared on Si(001) substrates with varying VHF power density ($P_{VHF})$, H$_{2}$ concentration and source ratio (NH$_{3}$/SiH$_{4})$. The results show that increasing H$_{2}$ concentration under the supply of a moderately large $P_{VHF}$, together with the adjustment of NH$_{3}$/SiH$_{4}$ ratio, enables us to prepare SiN$_{x}$ showing reasonable stability against a buffered hydrofluoric acid solution in spite of the very high deposition rate of 130 nm/s. The achievement of such a high-rate deposition at room temperature is primarily due to the significant enhancement of both gas-phase and surface-phase reactions in AP-VHF plasma. [Preview Abstract] |
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CTP.00184: Formation mechanism of indium-zinc-oxide film using RF magnetron sputtering based on optical diagnostics of gas phase Takayuki Ohta, Mari Inoue, Naoki Takota, Masufumi Ito, Masaru Hori TCO (transparent conductive Oxide) film has been used as transparent conducting electrodes of optoelectronic devices such as flat panel display, solar cells, and so on. As increasing the demand of high quality TCO film, various TCO film has been intensively investigated as promising alternatives Indium Tin Oxide (ITO). The advantages of Indium-Zinc-Oxide (IZO) are wide process window, chemical stability, high surface smoothness, and so on. Diagnostics of plasma is important for controlling sputtering process precisely and clarifying the formation mechanisms of thin films. The absolute densities of Zn and In atom were simultaneously measured by an absorption spectroscopy employing the compact multi-micro hollow cathode light source. Their densities were measured to be 10$^{8}$ from 10$^{9}$ cm$^{-3}$ and increased with an increase in the pressure. The behavior of In/Zn concentration ratio in the film measured by XPS corresponded to that of the absolute density in plasma. At RF power of 50 W and pressure 0.8 Pa, the optical transmission was more than 80 {\%} in the region of 400 to 800 nm and the low resistivity of 10$^{-3}$ to 10$^{-5} \quad \Omega $cm was obtained. [Preview Abstract] |
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CTP.00185: Incorporation Effects of Nitrogen into Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films by Physical Vapor Deposition Tsuyoshi Yoshitake Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon (UNCD/a-C:H) composite films were deposited in nitrogen and hydrogen mixed atmospheres by pulse laser deposition using a graphite target. The existence of UNCD crystallites in the film with a nitrogen content of 7.9 at.{\%} was confirmed from the XRD measurement. The UNCD crystallite size was estimated to be 2 nm using Scherrer's equation. The value is smaller than that (5 nm) of undoped films. From the Fourier transform infrared (FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectra, it was found that the chemical bonding formation of nitrogen atoms with carbon atoms accompanies with an increase in the amount of sp$^{2}$-bond. The film possessed n-type conduction with an enhanced electrical conductivity of 18 $\Omega ^{-1}$cm$^{-1}$ at 300 K. A heterojunction consisting of p-type Si and n-type nitrogen-doped UNCD/a-C:H composite exhibited a typical rectification action with a low leakage current. The result indicated that nitrogen atoms are chemically bonded in the UNCD/a-C:H composite film and they strongly influence both the structural and electrical properties. [Preview Abstract] |
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CTP.00186: Atmospheric pressure deposition of metal oxide films by an DC Arc Plasmatron Oleksiy Penkov, Vadim Plaksin, Heon-Ju Lee The effect of the deposition parameters on the structure and properties of ZnO films deposited by DC arc plasmatron at the atmospheric pressure was studied. The varied parameters were gas flow rates, precursor composition, substrate temperature and post-deposition annealing temperature. Vapor of Zinc acetylacetone was used as source materials, oxygen was used as working gas and argon was used as the cathode protective gas and a transport gas for the vapor. The plasmatron power was varied in the range of 700-1500 watts. Flow rate of the gases and substrate temperature rate were varied in the wide range to optimize the properties of the deposited coatings. After deposition films were annealed in the hydrogen atmosphere in the wide range of temperatures. Structure of coatings was investigated using XRD and SEM. Chemical composition was analyzed using x-ray photoelectron spectroscopy. Sheet conductivity was measured by 4-point probe method. Optical properties of the transparent ZnO-based coatings were studied by the spectroscopy. It was shown that deposition by a DC Arc plasmatron can be used for low-cost production of zinc oxide films with good optical and electrical properties. Sheet resistance of 4 Ohmscm was achieved after the deposition and 30 min annealing in the hydrogen at 350\r{ }C. Elevation of the substrate temperature during the deposition process up to 350\r{ }C leads to decreasing of the film's resistance due to rearrangement of the crystalline structure. [Preview Abstract] |
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CTP.00187: Temperature-Dependent Interlayer Couplings in Fe$_{3}$Si/FeSi$_{2}$ multilayers prepared by facing targets direct-current sputtering Shin-ichi Hirakawa, Ken-ichiro Sakai, Kaoru Takeda, Tsuyoshi Yoshitake Fe$_{3}$Si (25 {\AA})/FeSi$_{2}$ (10 {\AA}) multilayers were grown on Si(111) substrates by facing targets direct-current sputtering (FTDCS), and the interlayer coupling induced between the ferromagnetic Fe$_{3}$Si layers were investigated at low temperatures. Antiferromagnetic (AF) coupling at room temperature was gradually weakened with a decrease in the temperature, and it finally became ferromagnetic (F) coupling or non-coupling at temperatures lower than 77 K. A reason for the change in the interlayer coupling should be due to the semiconducting FeSi$_{2}$ interlayers. We consider that the reduction in the carrier concentration with the decrease in the temperature gradually weakened the AF interlayer coupling and finally extinguished it. [Preview Abstract] |
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CTP.00188: Deposition of MgF$_{2}$ thin films by pulsed laser ablation technique Alessio Perrone, Antonella Lorusso, Francesco Gontad In this paper, we report the successful growth of MgF$_{2}$ thin films on Si and zaffire substrates at room temperature by laser ablation of a pure MgF$_{2}$ target. The irradiations were performed at high vacuum (10$^{-5}$ Pa) using the forth harmonic of a Nd:YAG laser with energy density of about 10 J/cm$^{2}$. Uniform films, with a good adhesion on the substrate were obtained. The average ablation and deposition rates resulted to be 2.2 $\mu $g/pulse and 0.3 {\AA}/pulse, respectively. Different diagnostic techniques were used to characterize the films deposited on Si substrate. Films deposited on zaffire were dedicated to optical characterizations. Mass spectrometry studies of the laser ablated material indicate strong correlation between the partial pressure of the chemical species present in the plume and the residual gas. Present interest in the deposition of MgF$_{2}$ thin films is related to their potential application as protecting coatings in photocathodes. [Preview Abstract] |
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CTP.00189: Characterization of copper nitride thin films deposited by DC magnetron reactive sputtering Davoud Dorranian, Laya Dejam, Elmira Solati, Amirhossein Sari The Cu$_{3}$N films were deposited on BK7 glass substrates by reactive direct current magnetron sputtering of a pure Cu target at various Ar and N$_{2}$ partial pressures at room temperature. X-ray diffraction measurements show a phase transition in preferred orientation of samples from (111) planes to (100) with increasing the partial pressure of nitrogen in working gas. Two forms of nodule like and conical surface structures were observed due to different amount of nitrogen. The surface resistivity was strongly affected by these two structures. Calculated band gap energy of the samples shows a sharp enhancement by increasing nitrogen content in working gas. [Preview Abstract] |
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CTP.00190: Diamond and DLC Thin Film Preparation by Microwave Plasma Chemical Vapor Deposition under the Open-Air Condition Masahiro Tanaka, Hidetsugu Yagi, Hideki Motomura, Masafumi Jinno A diamond thin film has attractive properties such as high hardness, large heat conductivity etc. And, a DLC film has also interesting properties such as hardness, lubrication, chemical inertness. Microwave plasma chemical vapor deposition (MWPCVD) is an effective method for producing such a thin film. However, the deposition rate of the conventional low-pressure MWPCVD is very low. Authors have succeeded to produce a diamond thin film on a Si substrate with high deposition rate ($\sim $100$\mu $m/h) under the open-air condition, i.e. under the atmospheric pressure and without chamber, using microwave plasma system with a torch (electrode) of coaxial structure. Since the system has open-air structure, vacuum system is not required, which results low cost. In this study, we investigate the relationship between the quality and the experimental conditions synthesizing the diamond and the DLC film. The diamond film is synthesized under the methane concentration of 3-8{\%}(CH4/H2 by volume) and the DLC film is synthesized under the methane concentration of above 10{\%}(CH4/H2 by volume). [Preview Abstract] |
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CTP.00191: Capacitively Coupled Plasma Source with Comb-Type Electrodes for Uniform Plasma Processing H. Toyoda, K. Kanetake, T. Hiramatsu, T. Matsuda, T. Kawaharamura, M. Furuta, T. Hirao Recently, electronic devices on flexible films have been given much attention, due to its flexibility, lightness and so on. To fabricate such devices, however, low temperature processing is required because substrates for flexible devices are mostly made from polymer films such as polyimide and so on. In general, film deposition at low temperatures is difficult due to low surface migration of deposition precursors. However, high density plasmas may have possibility for such film deposition due to high flux of precursors and moderate ion irradiation on the film-depositing surface. In this study, a capacitively coupled plasma source with comb-shaped electrodes is developed for low temperature plasma enhanced chemical vapor deposition aiming at fabrication of flexible electronic devices. Application of the parallel magnetic field contributed to the increase in the plasma density and relatively high-density plasma 3x10$^{10}$ cm$^{-3})$ was obtained with low power density of 0.4 W/cm$^{2}$. Spatial profile of the plasma density is measured and uniform plasma production was confirmed. The result suggests that the present plasma source has capability of low-temperature thin film deposition with one-dimensionally long plasma production for roll-to-roll plasma processing. [Preview Abstract] |
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CTP.00192: ABSTRACT WITHDRAWN |
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CTP.00193: The effect of aluminum oxide layer on the morphologies of Al coatings prepared by reactive sputtering Jae-In Jeong, Ji-Hoon Yang, Seung-Hyun Jang, Hye-Sun Park Aluminum oxide (Al-oxide) films have been deposited by reactive un-balanced magnetron sputtering and applied to the morphology change of Al thick coatings. First of all, Al-oxide sputtering conditions were optimized in reactive sputtering by varying the deposition parameters prior to coatings. The formation of Al-oxide film was confirmed from the binding energy shift measured by electron spectroscopy for chemical analysis. The Al-oxide films were applied to change the morphology of Al film. 3 types of coating structures were designed and prepared on Nd magnet by magnetron sputtering, and the structure change has been investigated The coating structures consist of (1) single Al coating, (2) modified coatings having oxide or plasma treated layer in the middle of coating structure, and (3) Al/Al-oxide multilayer coatings. Surface and cross-sectional morphologies showed that Al/Al-oxide multilayer grew as a layered structure, and that very compact Zone III like structure were formed. X-ray diffraction peak showed that the crystal orientations of multilayer coatings were similar to that of the bulk powder pattern. Hardness increased drastically when the Al thickness was around 1$\mu $m in the Al/Al-oxide multilayer. [Preview Abstract] |
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CTP.00194: Synthesis of High Quality SiO$_{2}$ Film by Capacitively-Coupled Plasma CVD with Comb-Type Electrodes Takahiro Hiramatsu, Tokiyoshi Matsuda, Toshiyuki Kawaharamura, Mamoru Furuta, Takashi Hirao, Koji Kanetake, Hirotaka Toyoda Recently, flexible displays with lightness and flexibility attract much attention as next generation displays. To achieve the flexible display, thin film transistors (TFTs) on a plastic substrate at low temperature should be fabricated. The low-temperature deposition of a gate insulator is one of the key technology for the low-temperature fabrication of TFTs. In this study, we design a capacitively-coupled plasma with comb-shaped electrodes for low-temperature deposition of SiO$_{2}$ films. The influences of the deposition parameters, such as the pressure and the distance between the substrate and the electrode, on the film properties of SiO$_{2 }$were investigated. The deposition rate increased with increasing the deposition pressure and decreasing the distance between the dielectric and the substrate ($D_{d-s})$. On the other hand, the BHF etching rate decreased as the deposition pressure and the $D_{d-s}$ decreased, indicating that the densification of the films was enhanced. The deposited SiO$_{2}$ exhibit good insulating properties, which were the cuurent density of 1.9 nA/cm$^{2}$ and the breakdown voltage of 7.4 MV/cm. These results indicate that the SiO$_{2}$ films deposited by a capacitively-coupled plasma CVD with comb-shaped electrodes can apply to the gate insulator of TFTs. [Preview Abstract] |
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CTP.00195: PLASMAS FOR LIGHT PRODUCTION |
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CTP.00196: Electric-discharge source of spontaneous UV radiation based on xenon and cesium bromide gas-vapor mixture Yuriy Shpenik, Miron Klenivskiy, Volodymyr Kelman, Yuriy Zhmenyak Paper presents experimental investigations on obtaining UV luminescence of XeBr* molecules (spectral maximum at 281~nm) at excitation of alternative nontoxic Xe -- CsBr vapor mixture by a longitudinal pulsed-periodic discharge. Under optimal conditions the spectral composition of discharge radiation in the UV region hasn't considerable distinctions from the high-efficiency XeBr- excilamp which contains toxic bromine gas. The parameters and features of a new active medium as well as it's capability to serve as a new exciplex XeBr* source of UV radiation as alternative to ecologically unsafe and harmful sources containing mercury or toxic halogen-carrier are discussed in the paper too. Based on our successful previous investigations we proposed and tested a new mixture of xenon with cesium bromide vapor. At excitation by a longitudinal pulsed-periodic discharge of a two-component Xe-CsBr mixture, an intense UV radiation from the discharge tube was observed. The analyses of the discharge emission spectrum structure shows that this band is a result of electron transitions from excited $B$ to ground $X$ states of exciplex XeBr* molecules which forming in the discharge plasma. [Preview Abstract] |
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CTP.00197: Calculation of argon-mercury mixture ionization coefficient in low-current glow discharge Gennady Bondarenko, Maxim Fisher, Vladimir Kristya Simulation of electron, ion and metastable motion and interactions in a low-current discharge in argon-mercury mixture used in gas-discharge illuminating lamps is fulfilled. Trajectories of electrons are calculated with the Monte Carlo method, whereas motion of ions and metastables is described on the basis of transport equations. The obtained dependence of the ionization coefficient (IC) on the mercury content in the mixture agrees with experimental data and shows that the IC reaches its maximum under the mercury relative density of the order of 0.001. It is found that the IC increase is mainly a result of Penning ionization of mercury atoms, and contribution of the Penning ionization into the IC increases under lower electric field strength. The discharge ignition voltage as a function of the interelectrode distance is also calculated. It is shown that for discharge in argon results correspond to experimental data and in argon-mercury mixture the ignition voltage has substantially lower value depending on the cathode ion-electron secondary emission rate and the gas temperature. [Preview Abstract] |
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CTP.00198: Measurement of the plasma temperature in HID-lamps by emission- and absorption-spectroscopy of Dy spectral lines M. Westermeier, C. Ruhrmann, A. Bergner, P. Awakowicz, J. Mentel To investigate physical effects like the emitter-effect in HID-lamps, it is essential to know the plasma temperature $T_{Pl}$ inside the burning arc plasma. Up to now $T_{Pl}$ was determined by measuring the absolute intensity of Hg spectral lines while assuming a saturated and constant Hg pressure inside the HID-lamp. Within this work, a special broadband absorption spectroscopy measurement by means of a powerful UHP-lightsource is combined with an absolutely calibrated measurement of the emission lines of Dy. Thus, the population density of the ground-state and of an excited energy state of the Dy atoms is determined. With the assumption of a Boltzman energy distribution, the Dy temperature can be calculated from this measurement which is equal to the plasma temperature $T_{Pl}$ in the LTE plasma of an HID-lamp. As this $T_{Pl}$ measurement is independent of the Hg-content it might be important for the investigation of Hg-free HID-lamps in the future. Results of the plasma temperature measurements in different YAG HID-lamps for high and low operating frequencies will be presented and compared to the results of former Hg-dependent measurements. [Preview Abstract] |
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CTP.00199: Investigation of the arc attachment at thoriated cathodes in a model lamp by measurement and simulation A. Bergner, M. Westermeier, C. Ruhrmann, J. Mentel, P. Awakowicz This paper deals with pyrometric temperature measurements at thoriated cathodes in a model lamp and the emitter effect of thorium which is induced by a thorium atom monolayer at the cathode end face. For that purpose the cathode is operated in the diffuse mode with direct current and the temperature is recorded by absolutely calibrated two-dimensional 1-wavelength pyrometry. Furthermore corresponding numerical simulations of the cathode temperature in dependence on the work function done by a commercial finite element solver are presented. They are compared with the experimental results to get a quantitative impression of the reduction of the work function and cathode temperature by the thorium monolayer. A physical explanation of the deposition of the monolayer is given by comparing anodic and cathodic current transfer. Thus it can be found that the work function of tungsten is reduced by 1.5\,eV by the emitter effect of thorium. [Preview Abstract] |
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CTP.00200: Discharge characteristics of micro-needle array diamond structure Takayuki Misu, Shimon Ono, Tsukasa Higa, Miki Goto, Toshihiko Arai Using the back-sputtering techniques, we examined to create micro-needle array of high aspect ratios on diamond substrate surfaces, and measured the discharge characteristics of the diamond electrodes. The roughness of diamond substrate surfaces was formed using O$_{2}$ gas plasma in a reactive ion etching (RIE) system. The power electrode materials of RIE were used both stainless steel and MgO sintered ceramic. The samples of diamond to be etched were positioned on the power electrode. The values of the secondary electron emission coefficient $\gamma $ were obtained by introducing the breakdown voltages measured into the self-sustained equation. The micro-needle array of high aspect on diamond substrate surfaces was fabricated by using back-sputtering from MgO electrode. The RMS roughness of diamond substrate surfaces in the case of MgO electrode is higher than those in the case of stainless steel electrode. The $\gamma $ value in the case of MgO electrode is about two times higher than those in the case of stainless steel electrode. [Preview Abstract] |
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CTP.00201: Investigation of the emitter effect in high intensity discharge lamps C. Ruhrmann, M. Westermeier, A. Bergner, J. Mentel, P. Awakowicz The improvement of lifetime is a particular interest of actual research into HID lamps. It can be achieved by a reduction of the temperature of the tungsten lamp electrodes being accomplished by the so called ``gas phase emitter effect.'' It is generated on the electrode surface by a monolayer of electropositive atoms of certain emitter elements (e.g. Ce or Dy) which are added to the lamp filling. This monolayer with dipole character reduces the effective work function and therefore the potential barrier for electrons leaving or entering the electrode. A quantification of the emitter effect is performed in front of the electrode by electrode tip temperature measurements as well as density measurements by means of absolutely calibrated optical emission and absorption spectroscopy. Spatial and phase resolved electrode tip temperature and density measurements of the emitter material in special research HID lamps will be presented for low and high frequencies. [Preview Abstract] |
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CTP.00202: UV Emission from Poly-Phase Nitric-Oxide Discharge/Plasma Confined by Multi-Pole Magnetic Field and Its Application Kazunori Matsumoto, Hidefumi Uchiyama, Hirofumi Ninomiya, Seiji Oda, Nobuyuki Nojima We have investigated experimentally an effect of a multi-pole magnetic field on UV-emission from molecular gases excited by a poly-phase ac discharge/plasma. It was found that when a nitric oxide gas NO mixed with a nitrogen molecular gas N$_{2}$ was used, an intense ultra-violet (UV) irradiation ranging from 200nm to 300nm was emitted from magnetically confined plasma-regions. Maximum UV emission was observed around 10{\%} concentration ratio of NO to N$_{2}$. The relation between UV emission characteristics and plasma parameters was studied by using a plane molybdenum probe. As a ratio of NO increased, electron density and temperature decreased. It seems that NO molecules dissipate plasma energy in order to emit UV lights. We have also applied this UV emitter to sterilizing powdered polysaccharides. This UV has shown a similar sterilization performance with the conventional low-pressure mercury UV lamp. This UV emitter is a candidate of a mercury free UV lamp that is applicable for various industrial processing such as a UV cure and a UV cleaning. [Preview Abstract] |
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CTP.00203: Caxial Microwave Discharge Lamp of Aluminum Coated Quartz Glass Tube Taiki Sakai, Akimitsu Hatta Caxial microwave discharge (CMD) lamp has been developed for UV light source. To extend the length of microwave plasma in the discharge lamp, a novel structure of microwave discharge lamp has been developed. The microwave plasma was produced in a thick quartz tube by traveling wave along a coaxial line consisting of a central plasma rod as the inner conductor itself and the Al coating on the tube surface as the outer conductor. A thin slit was opened on the outer conductor of Al coating along the tube to extract the emitted light. The microwave plasma length was extended more than 75cm at 150 W of microwave power. Peak emission intensities showed gradual decay with the traveling distance of the microwave from the end while the white band emission originated from recombination showed rapid decay from the excited end. Emission profile along the lamp was almost uniform when the microwave was supplied from both sides alternately. [Preview Abstract] |
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CTP.00204: Uniformity in length of carbon nanotwists by filament discharge treatment for stable field electron emission Yoshiyuki Suda, Yuki Sugioka, Hideto Tanoue, Hirofumi Takikawa, Hitoshi Ue, Yoshito Umeda, Kazuki Shimizu We have shown that a helical carbon nanofiber, carbon nanotwists (CNTws) on substrate are made to stand up by dielectric barrier discharge (DBD) treatment and this enhances their field emission property [1]. In this study, we present that the height of CNTws on substrate became uniform by the DBD treatment. CNTws with ethyl cellulose and silicone binders were printed on indium-tin-oxide-coated glass substrate [2]. The CNTws-coated substrate was treated by DBD in nitrogen atmosphere for 30 sec. The gap length of the DBD apparatus and nitrogen gas flow rate were 1 mm and 2 L/min, respectively. The CNTw amount in the binders ($A_{CNTw})$ was varied between 2.5 and 20 phr. Stand up of CNTws were seen when $A_{CNTw}$ was $\ge $ 5 phr. The length of CNTws on substrate ($L_{CNTw})$ at $A_{CNTw}$ = 10 phr was $\sim $4.5 $\mu $m, and the tip heights were not uniform. This unevenness was improved at $A_{CNTw} \quad \ge $ 15 phr. The field emission property of the CNTws at $A_{CNTw}$ = 20 phr was measured to be threshold electric field of 3.9 V/$\mu $m and highest emission current density of 630 $\mu $A/cm$^{2}$. [1] Yuji Hosokawa, et al, J Phys. D, 41 (2008) 205418 [2] Yuki Sugioka, et al, Jpn. J. Appl. Phys., submitted [Preview Abstract] |
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CTP.00205: Optical characterization of a point-plate microplasma A.J.M. Pemen, T. Huiskamp, E.J.M. van Heesch A microplasma is created in a point-plate setup where the point electrode is grounded and the plate electrode is covered by a dielectric substrate, e.g. a foil or thin film. The plasma is used to create patterns on the dielectric. In this paper we will analyze which parameters affect the spot size as created on the dielectric. Unipolar high voltage pulses ($<$ 4kV) were applied to the plate electrode to investigate plasma diameter dependency on the applied voltage (polarity and amplitude) and the gap distance ($<$1mm). The plasma spot size was determined from time and spatial resolved ICCD imaging. It was concluded that the amplitude of the applied voltage, albeit positive pulsed, negative pulsed or AC, was the key parameter on which the spot size depended. The lowest possible applied voltage resulted in the smallest plasma size. Gap distance was also a parameter with regard to the spot size. This was most pronounced for large gap distances ($>$300$\mu $m). For smaller gap distances there was no clear dependence. The main conclusion is: to make the spot size as small as possible the applied voltage should be just above the extinction voltage, the gap distance should be around 50-150$\mu $m and the electrode should be as sharp as possible. Furthermore, the smallest spot size recorded was 50$\mu $m. [Preview Abstract] |
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CTP.00206: Atmospheric Pressure Micro Inductively Coupled Plasma Source with Floating Electrode Minoru Sasaki, Hiroki Matsuyama, Shinya Kumagai, Masaru Hori Atmospheric pressure micro-ICP source is realized. Cu coil electrode and trench are prepared by milling glass epoxy substrate. U-shaped coil electrode is 9mm wide and 50mm long. Plasma ignition is promoted with the floating electrode placed inside the channel for the gas flow. Micro-ICP is generated at $\sim $35W of 100 MHz with He gas flow. In the spectra, O and OH peaks are observed in addition to He or Ar peaks, but metal (W) or C peaks are not observed. The device shows durability against $>$5h operation. [Preview Abstract] |
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CTP.00207: A three-dimensional hybrid simulation with electron-fluid and ion-particle model for micro dielectric barrier discharges Seung Bo Shim, In Cheol Song, Min Sup Hur, Ho-Jun Lee, Chung-Hoo Park, Hae June Lee A plasma display panel (PDP) is a good example of a micro dielectric barrier discharge. A numerical simulation is good way to investigate the discharge characteristics in a PDP cell because experimental diagnostics is difficult in this small cell. In a high pressure gas discharge, a fluid model with a drift-diffusion approximation is a most practical method. However, drift-diffusion approximation is not applicable to heavy ion motions even at a high pressure in PDP operation. Especially, Xe ion motion is overestimated in the fluid code. A threedimensional hybrid simulation has been developed to combine a fluid model for electrons and a particle-in-cell model for ions. Discharge characteristics were investigated using the hybrid model such as the electric field intensity, and energy and angle distributions of the ions at the boundary. It was proved by the comparison of the infrared light emission that the hybrid model represents experimental results very well while the fluid model does not Also, the difference between the hybrid and the fluid code is more significant in a three-dimensional code than that in a two-dimensional code. [Preview Abstract] |
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CTP.00208: BASIC PLASMA PHYSICS PHENOMENA IN LOW-TEMPERATURE PLASMA |
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CTP.00209: AC (20kHz) excited plasmas in contact with liquid Jingjing Liu, Michael Kong Dynamic interaction of ionized gases with liquid has been an active research area because of the considerable scope and depth of its underpinning science, examples of which include sonoluminescence and co-existence of phases (e.g. gas, liquid, solid and ionised gases). There are normally two major types of liquid-plasmas, namely above-liquid plasmas and in-liquid plasmas, the former being generated in a relatively stationary gas environment above the gas-liquid interface and the latter being generated within the liquid usually in gas bubbles.Electrical and optical characteristics of 20 kHz needle-water electrode plasmas are investigated in this paper. There are two working states: pulse state and steady state. Plasmas extinguish when the voltage polarity changes in the pulse state. It makes plasmas require high re-breakdown voltage in the next half cycle where the big pulse forms. However, there are some species left in the gap while plasmas quench, this makes the re-breakdown voltage much lower than the initial one. In the steady state, plasmas are more intense and always exist in the discharge gap, although they are weak during the voltage polarity change period. The remaining charges help re-develop plasmas in the next cycle. Plasmas influence the water property such as pH, conductivity and water due to the chemical reactions. [Preview Abstract] |
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CTP.00210: Study on Nonlinear Resonance of Electron Heating in Asymmetric Capacitive Discharges with a Time-Dependent Fluid Sheath Model Zhong-Ling Dai, You-Nian Wang Recently, it has been found that a nonlinear electron resonance effect can effectively enhance not only the ohmic but also stochastic heating in asymmetric capacitive discharges. Some authors have studied the effects of the plasma series resonance by means of a nonlinear global model with a constant sheath thickness. In fact, the sheath boundary varies with time periodically in rf discharges. In the work, we adopt a time-dependent fluid sheath model to describe nonlinear series resonance effects. With the model, we can determine selfconsistently the relationship between the instantaneous potential drop across the sheath and the instantaneous sheath thickness. The numerical results demonstrate that the self-excitation of the plasma series resonance significantly enhances both Ohmic heating and stochastic heating. Also, we observe that the effects of nonlinear series resonance increase the total power dissipation by factors of 2--5 for low pressure plasmas. [Preview Abstract] |
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CTP.00211: Characteristics of helium/water vapour jet plasmas Jingjing Liu, Michael Kong Stable low-temperature plasmas which possess abundant chemically reactive species (nitrogen and oxygen related species) are required for biomedical applications such as wound disinfection and healing. A needle-ring DBD plasma jet with flowing helium gas is used in this paper to achieve the low gas temperature plasmas. Water vapour is mixed in the flowing gas in order to produce more oxygen and hydrogen related active species in the plasmas.Electrical and optical characteristics of the helium/water vapour jet plasmas are studied. There are four different modes of the plasmas, among which the bullet mode and arc mode without voltage distortion are particularly investigated. Bullet mode will disappear while the moist helium flow rate is higher than 300sccm. Higher moist helium flow rate results in slower bullet velocity and weaker bullet intensity. Active species production in both bullet and arc modes increases with adding modest water vapour in the gas mixture, but decrease with further more water vapour. Rotational, vibrational and excitation temperatures are all influenced by the moist helium flow rate. Electron density plays significant role in producing the active species in bullet mode. Water vapour concentration together with the electron density in arc mode affects the active species generation. [Preview Abstract] |
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CTP.00212: Investigation of an atmospheric pressure helium plasma jet with floating ground bare metal nozzle Wen-Chao Zhu, Dirk Luggenh\"olscher, Wen-Cong Chen, Feng Xie, Fei-Xiang Liu, Yi-Kang Pu APPJ generated in a quartz capillary tube with kHz power has been attracting significant attention for the ``bullet-like'' form that composed of the propagating ionization front. A plasma jet with a floating ground bare metal electrode at the nozzle is reported here. A simple current probe method and an optical emission method using a high-speed photodiode are used to investigate the temporal behavior of the bullet propagation. By measuring the spatial and temporal jet current and optical emission, we show that the plasma jet launched outside the nozzle is formed by the charge accumulation on the floating ground electrode after the dielectric barrier discharge between the two electrodes. The propagation mechanism of the plasma jet is similar to the positive glow corona discharge. [Preview Abstract] |
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CTP.00213: Secondary Ionization Coefficient of MgO and Accumulated Charge Takashi Sekizawa, Susumu Suzuki, Yasuhide Kashiwagi, Haruo Itoh An investigation of Townsend's secondary ionization coefficient $\gamma $ of MgO is carried out experimentally [1-3] using the breakdown voltages and Townsend's criterion. An investigation by the V-Q Lissajous figure method [4] is also carried out to determine the breakdown voltage $V_{s}$ of a MgO film electrode at frequencies up to 2 kHz, considering the effect of the accumulated charge on the MgO film electrode. From the results, $\gamma $ that considers the effect of the accumulated charge is larger than $\gamma $ in which the effect of the accumulated charge is not considered. Furthermore, we found that the $\gamma $ of MgO is larger than the $\gamma $ values of metallic electrodes. On the other hand, it is evident that no accumulated charge effect appeared at frequencies lower than 50 Hz of the applied sinusoidal voltage, because the decay of the accumulated charge on the MgO film electrode vanished with a time constant of about 40 ms in this case. More detailed studies including the other dielectric electrode are being carried out. [1] S.Suzuki and H.Itoh, 2004 \textit{Jpn.J.Appl.Phys.}, \textbf{43}, 10, 7234-7239. [2] S.Suzuki and H.Itoh, 2007 \textit{Jpn.J.Appl.Phys.}, \textbf{46}, 1129-1136. [3] S.Suzuki and H.Itoh, 2009 \textit{IEEJ Trans. FM}, \textbf{129}, 909-914 [in Japanease]. [4] K.Teranishi, N.Shimomura, S.Suzuki and H.Itoh, 2009 \textit{Plasma Sources Sci. Technol.}, \textbf{18}, 045011. [Preview Abstract] |
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CTP.00214: Decomposition of $m$-xylene by $N_2 (A^3\Sigma _u^+ )$ and thin film deposition Susumu Suzuki, Mitsuo Shimozuma, Haruo Itoh The study has carried out on the determination of the collisional quenching rate coefficient of $N_2 (A^3\Sigma _u^+ )$ by $m$-xylene (C$_{8}$H$_{10})$, which has the weakest bonding strength among the three isomers of xylene. In our first attempt, the collisional quenching rate coefficients of $N_2 (A^3\Sigma _u^+ )$ by xylene ($o$-xylene, $m$-xylene, and $p$-xylene) have not yet been reported to the best of the authors' knowledge. The diffusion coefficient $D_{m1 }$of $N_2 (A^3\Sigma _u^+ )$ in N$_{2}$/(1ppm) $m$-C$_{8}$H$_{10}$ mixtures and the collisional quenching rate coefficient $k$' of $N_2 (A^3\Sigma _u^+ )$by $m$- xylene is determined as 151.5$\pm$0.7 cm$^{2}$/s and (4.4$\pm$0.6)$\times$10$^{-9}$ cm$^{3}$/s, respectively. Surprisingly, it is found that any by-product of xylene is deposited on the cathode, through repeated experiments, and then the current-voltage curves consistently shift to the higher-$E$/$p_{0}$ region. For the purpose of clarifying the reason behind this behavior, we have confirmed that these changes in the current-voltage curves are caused by the thin-film deposition of a by-product of decomposed xylene on the cathode surface by Auger electron spectroscopy. [Preview Abstract] |
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CTP.00215: Hysteresis through E-H and H-E transitions in Ar-ICP using space- and time-resolved optical emission spectroscopy Yo Mitsui, Hayashi Yuichirou, Tetsuya Tatsumi, Toshiaki Makabe Inductively coupled plasma (ICP) has two sustaining modes according to the plasma external condition, such as input power, gas pressure, etc. One is inductive H-mode, where high density plasma is generated by electromagnetic field. The other is capacitive E-mode, where plasma is ignited by static electric field between segments of a current coil. In our previous paper, we studied the static and dynamic optical characteristics during E-H transition. Hysteresis characteristics of the emission intensities of Ar(2p$_{1})$ and Ar(2p$_{9})$ through E-H and H-E transitions in Ar-ICP was studied by using space- and time-resolved optical emission spectroscopy (OES). The 2D-t emission images of Ar(2p$_{1})$ produced by high-energy electrons were quite different from those of Ar(2p$_{9})$ mainly by low-energy electrons. Local non-uniformity of the OES in Ar(2p$_{1})$ was essential during the E-mode. On the other hand, the spatial distributions of both Ar(2p$_{1})$ and Ar(2p$_{9})$ were uniform during H-mode and H-to-E transition. The metastable Ar(1s$_{5})$ with a long lifetime has the effective contribution to keep the H-mode up to a lower coil current region in the H-to-E transition. [Preview Abstract] |
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CTP.00216: Measurement of the Density Distribution of the Non-emissive Ar Metastable State in a 2f-CCP by Using OES with a Pair of Emission Lines Kazuki Takahashi, Tomihito Ohba, Tetsuya Tatsumi, Takashi Yagisawa, Toshiaki Makabe Two-frequency capacitively coupled plasma (2f-CCP) has been widely used for SiO2 etching processes in industry. The argon gas plays an important role in 2f-CCP, not only to dilute fluorocarbon gas which is reactive for SiO2 etching, but to sustain plasma partly by a stepwise excitation through a metastable state. Non-emissive argon metastable has been measured conventionally by using a method with eternal light sources, such as laser absorption spectroscopy (LAS) and laser-induced fluorescence (LIF). When a pair of short- and long-lived excited states is coupled with upper resonant state, it will be possible to determine the density of long-lived lower state from OES of the upper state. We measure the spatial distribution of metastable Ar(1s5) density in a 2f-CCP in pure Ar by OES aided with CT technique. Our method is validated by the comparison between Ar(1s5) density measured by OES and LAS. The majority of the metastable production is observed at the region close to the edge of electrodes, resulting in the radial nonuniformity of the density distribution of Ar(1s5). [Preview Abstract] |
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CTP.00217: Time-dependent of recombining Plasma with Pulse Plasma flow Takashi Torada, Akira Tonegawa, Naoki Mine, Hiroyasu Komukai, Tomohiko Ono, Kazutaka Kawamura The time evolution of electron density n$_{e}$, electron temperature T$_{e}$, electron velocity distribution function \textbf{\textit{?}}$_{e}(\upsilon)$, and hydrogen Balmer series spectra is found to depend on gas pressure in the recombination plasma with pulse plasma flow. The pulse plasma flux is generated by controlling the electric circuits of electrodes of plasma source. The negative spikes were appeared in the time evolution of the Balmer series spectra, which indicate on the transition from ionizing to recombining plasma. [Preview Abstract] |
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CTP.00218: Nonambipolar electron fluxes in 2D unmagnetized inductively coupled plasma Eugene Bogdanov, Anatoly Kudryavtsev, Lev Tsendin It is generally accepted that electron and ion fluxes in unmagnetized, current-free plasmas obey the ambipolar diffusion, i.e., that electron and ion flux densities in the quasineutral plasma are equal and hence the total current in the plasma is zero. This scenario originates from a well-known one-dimensional analysis performed by Schottky. But the real plasma objects are a two-or three-dimensional when as the plasma density and the electron temperature is spatially inhomogeneous. As it was pointed in [Rozhansky A.V., Tsendin L.D. Transport Phenomena in Partially Ionized Plasma. Taylor and Francis. 2001], in a 2D plasmas where both the density and the electron temperature are disturbed, it is impossible to create the potential electric field which equalizes the electron and ion fluxes everywhere in a plasma volume [1]. It means that the considerable radial electron vortex current arises which doesn't obey the ambipolarity condition je(x,r) = ji(x,r). Our 2D fluid simulations of ICP discharges in argon and oxygen show that electron flux always has a large vortex component as in the case of conducting and insulating walls. It means that in inhomogeneous 2D discharges electron transport is never ambipolar. [Preview Abstract] |
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CTP.00219: Plasma phase-space fluctuations Fred Skiff, Vikram Patel, Dereth Drake The low frequency electrostatic, kinetic, electromechanical degrees of freedom of weakly collisional plasma are studied through the measurement of correlation functions that are resolved in the ion phase-space using laser-induced fluorescence. Fluctuations in a CW magnetized cylindrical plasma column of n $\sim $ 10$^{9}$ cm$^{-3}$ singly ionized Argon produced by an inductively coupled source are observed using two movable periscopes that image 10mm$^{3}$ laser-illuminated volumes which can be translated along the magnetic field direction (the cylinder axis). Two-point correlation functions are be obtained which provide information on the linear and nonlinear dynamics of the ion degrees of freedom. [Preview Abstract] |
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CTP.00220: VUV spectroscopic diagnostics of the vibrational temperature to the ground state of hydrogen molecules in recombination plasma Takaaki Iijima, Akira Tonegawa, Tomohiko Ono, Takashi Torada, Kazutaka Kawamura The vacuum ultraviolet (VUV) spectroscopic method has been evaluated for measuring of the vibrational temperatures T$_{vib}$ of H$_{2}$ to the electronic ground state in hydrogen recombination plasma. This is inferred from the comparison of simulated Lyman, Werner spectra for H$_{2}$ taking into account radiation trapping effects with measured VUV spectra in the range from 90 to 150 nm. T$_{vib}$ of H$_{2}$ is around 4000-5000K in hydrogen plasma at the discharge current of 50 A and electron temperate of 10 eV. With increasing the gas pressure, T$_{vib}$ decreases and remains constant at 1000 K in the recombination plasma. [Preview Abstract] |
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CTP.00221: Tomographic Analysis of a Plasmoid in Supersonic MW Post-Discharge Milka Nikolic, Ana Samolov, Svetozar Popovic, Alex Godunov, Leposava Vu\v{s}kovic The tomographic analysis was used for reconstruction of local plasma parameters of a plasmoid in the post-discharge region of an Ar supersonic MW discharge. The supersonic flow was generated using a convergent-divergent nozzle upstream of the discharge region [1]. A cylindrical cavity was used to sustain a discharge in the pressure range of 100-600 Pa. Evidence of plasma rotation was observed. We defined the numerical method based on the inversion of the Abel integral equation for a cylindrical cavity. Optical emission spectroscopy measurements were taken under two mutually perpendicular directions for evaluation of the spatial distribution of the excited species in the plasmoid region.\\[4pt] [1] Drake, D. J., S. Popovic, and L. Vu\v{s}kovic, J. Appl. Phys. \textbf{104}, 063305 (7pp) (2008). [Preview Abstract] |
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CTP.00222: The validation of oxygen optical actinometry using laser-induced fluorescence Samir Keckar, Jim Conway, Paul Swift, Stephen Daniels In reactive ion etch processes radicals such as O play a major role in the process outcome due to their high reactivity. It is therefore of crucial importance that the precise oxygen density is measured for an improved understanding of plasma-induced processes. Reported on here is the determination of absolute atomic oxygen density within oxygen plasma using laser-induced fluorescence (LIF) as the diagnostics technique. The plasma investigated is a capacitively coupled RF discharge operating at 13.56MHz, Plasmalab System100. A two-photon absorption laser-induced fluorescence (TALIF) technique is used 2*225nm to avoid the challenging generation of high energy photons required for the single photon LIF 130nm. A calibration method is employed which enables the calculation of the O concentration without the need to know the spatial and intensity profile of the laser beam. However, it is also possible to infer radical concentration from a comparative measurement the intensities of selected spectral emission lines from OES data, this technique is called optical actinometry. The results of this project using the TALIF scheme will be used as a benchmark to validate the much simpler actinometry technique. [Preview Abstract] |
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CTP.00223: Temperature and energy evolution of nanosecond repetitively pulsed discharges in air at atmospheric pressure Farah Kaddouri, David Z. Pai, Gabi D. Stancu, Deanna A. Lacoste, Christophe O. Laux Nanosecond repetitively pulsed (NRP) discharges have been widely studied this last decade for different applications: plasma assisted combustion, bio-medecine and aerodynamic flow control. We are interested in the effect of NRP discharges on combustion, namely on the mechanism of stabilization of lean premixed flames. NRP discharges were generated in a pin to pin configuration at atmospheric pressure in preheated air at 1000 K by high voltage (6.3 kV) pulses of 10-ns duration applied at a repetition frequency of 10 kHz. Our interest was to focus on the impact of the excited nitrogen densities on the heat release. Gas temperature (Tg) measurements have been performed. We compared this temperature profile to the one obtained by calculations. In these calculations we also evaluate the contribution of each excited nitrogen state to the increase of the gas temperature. We obtain good agreement between the measurements, which show a very fast increase of Tg from 1500K to 2800 K in 10 ns, and the calculations. N2 (B) is shown to have the major contribution (about 85{\%}) to this fast heating process. [Preview Abstract] |
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CTP.00224: Movement of Plasma Components Thrown from a Small Slit into a Cylindrical Container Masaaki Kato, Yohei Kobayashi, Masanari Matsumoto, Takahiro Shimizu, Takeo Ohte We made some containers as models of the narrow space with small slit, and studied the movement of plasma estimating the reached components inside the containers. Comparing differences of contact angle before plasma treatment with after that, the quantity of the plasma reached to that place is estimated. The treatment power and time change the quantity of the plasma into these containers. In cylindrical containers, the differences of contact angle were almost symmetrical from the point of the slit. The plasma components in the container behave toward every radius by same motion. Near the slit there is the biggest change of the contact angle in all points inside the container, and far from the slit, the changes become smaller. We get that the modification degree inside the containers is described by the distance from the slit. Changing the slit length, when the length is long, the quantity of plasma is small. The spread of the plasma is almost similar in each length. The slit length does not change the behavior of plasma thrown into the container, but change the quantity. The longer the slit length is, the later the time introducing plasma components will be. The surface modification sources are ions and radicals mainly. Both ions and radicals operate the modification and relate to the behavior inside these containers. [Preview Abstract] |
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CTP.00225: Kinetic Alfv\'{e}n Wave Excitation by magnetosonic Wave in Plasmas Sanjay Kumar, R.P. Sharma This paper presents the model equations governing the nonlinear interaction between dispersive Alfv\'{e}n wave (DAW) and magnetosonic wave in the high-$\beta$ plasmas ($m_e / m_i \ll \beta$ ; known as kinetic Alfv\'{e}n waves (KAWs); here $\beta = 8 \pi n_0 T/B_0^2$ is thermal to magnetic pressure, is $n_0$ unperturbed plasma number density, $T(=T_e \approx T_i )$ represents the plasma temperature, and $m_e (m_i )$ is the mass of electron (ion)). This nonlinear dynamical system may be considered as the modified Zakharov system of equations (MZSE). These model equations are solved numerically by using pseudo-spectral method to study the nonlinear evolution of the KAW turbulence in solar wind at 1AU. We observed the nonlinear evolution of KAW magnetic field structures having chaotic behavior associated with the magnetosonic wave. Relevance of these investigations to the high-$\beta$ plasmas in solar wind has been pointed out. The acceleration of the solar wind may be produced by the coupling of KAW and magnetosonic wave via filamentation process as discussed here. [Preview Abstract] |
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CTP.00226: THERMAL PLASMAS |
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CTP.00227: Analysis of dynamic states of discharge channels between plasma jets in AC electric arc Tomasz Daszkiewicz The article presents the results of the 3-D simulation of discharge channel displacement during one half-period of AC electric arc at Im=500A and Im=80A with the Fluent program indicate that the obtained pictures of the phenomenon are qualitatively similar to the pictures recorded with an high-speed digital camera Photron, and the computer simulation enables much more comprehensive analysis of the phenomenon. In addition to the selected frames of arc simulation and the corresponding distributions of temperature and current density vectors on a plane, the distributions of temperature, current density and matter velocity values on the axis of the electrode arrangement model are presented. The composite motion (continuous and jumping) of discharge channels was analyzed taking into account the displacement of mass and changes of matter states. [Preview Abstract] |
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CTP.00228: A study on a new material to replace the thoriated-tugsten electrode Tadao Uetsuki, Akira Matsuo, Katsuyuki Morii, Hisao Hatanaka ThO2-W is popularly used for the electrodes of a super-high pressure mercury lamp used in semi-conductor processing. This is because the work function of ThO2-W is much lower than that of the tungsten, therefore its electron emission performance is excellent compared with tungsten. However, ThO2-W is not desirable for the global environment because of its radioactivity. Therefore it would be very useful to make a new non-radioactive material to replace ThO2-W as the electrode, and many research efforts have been attempted for this purpose. However, the materials which were researched till now could not improve upon ThO2-W lifetime when they were used as the electrode in the lamp. This means these materials have higher work function than ThO2-W. The higher work function causes higher electrode temperatures, leading to faster evaporation of the electrode material and shorter lamp life. The purpose of our research is to make a new electrode material having better performance than ThO2-W. We have studied which oxide is best by controlling the particle radius or the volume of metal oxides mixed into the tungsten. In this paper we report the results obtained by studying Nd2O3-W and Sm2O3-W as the electrodes of a super-high pressure mercury lamp used for the semi-conductor processing. [Preview Abstract] |
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CTP.00229: Visualising heated gas in an RF plasma loudspeaker Y.C. Sutton, P.C. Johnson, D.B. Sharp, G.V. Naidis, N. St.J. Braithwaite, J. Moore An ac modulation (here in the audio frequency range) of the electric field in an RF atmospheric pressure air plasma gives rise to a modulation in the temperature and dimensions of the gas volume. As in natural lightning, the gas heating in the ionised column causes external pressure variations. This electro-acoustic transduction has been used to make a loudspeaker. Spatial and temporal measurement of the gas temperature can identify the nature of the thermal expansion and provides a direct approach to understanding its relationship to the sound pressure wave that is generated. Spectroscopic measurement of rotational line emission from nitrogen molecules is limited to the main current channel where there is optical emission from excited nitrogen molecules. The wider picture is revealed through the use of time-resolved Schlieren method where the refractive index gradients caused by gas heating in the plasma are imaged. Results show the gas heating extends far beyond the main current-carrying channel, in line with numerical modelling of the steady state. Convection and diffusion further interact with the modulation in the mechanism of sound generation. [Preview Abstract] |
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CTP.00230: Net emission coefficients of argon-iron plasmas Martin Wendt, Heinz Sch\"{o}pp, Dirk Uhrlandt This work presents net emission coefficients for argon-iron plasmas for temperatures from 3000 to 30000~K and iron fractions from 0 to 100~\%. Net emission coefficient avoid the numerical costs of an exact treatment of the radiation transport equation for elements with a multitude of spectral lines, so that the results presented here are useful for the modelling of welding arc. Next to spectral lines the results presented here take into account free-free and bound-free transitions. The broadening of the spectral lines is dominated by quadratic Stark broadening. Their Stark widths are calculated using semiclassical broadening theory. For each species a mean scaling factor for the Stark widths is determined by comparison with published experimental Stark widths measured at several electron densities and temperatures. Additionally, calculated side-on spectral radiances are compared with measurements from a gas metal welding arc. The presented results are in good agreement with previous net emission coefficients for argon-iron plasmas. [Preview Abstract] |
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CTP.00231: Optical measurements of gas temperatures in Ar/CO$_{2}$ arc plasma Nuno Cerqueira, Karl Kesseng, Charles de Izarra This paper presents an experimental study of the temperatures on DC vertical short free arc in Ar and Ar/CO$_{2}$ mixtures by employing optical interferometry and optical emission spectroscopy. The arc plasma burns between two tungsten vertical electrodes with a gap of 10 mm put in a chamber filled with argon or an argon/carbon dioxide mixture at atmospheric pressure. Two optical windows allow to observe the arc plasma in the chamber. Electrical power is delivered by a DC high voltage (10 kV) with a current intensity chosen from 0,1A up to 0.3 A. By employing optical interferometry, acquired interferograms were treated using Fast Fourier Transform and Abel inversion to obtain the radial distribution of the plasma index refraction. Temperature profiles were then obtained from Gladstone-Dale relation, taking in account the plasma composition versus temperature. The experimental spectrums of the Swan band of C$_{2}$ molecule have been recorded and a code of calculation has been created to simulate molecular spectra of the radical C$_{2}$. Finally rotational temperatures have been determined by comparison between experimental and calculated spectra and then temperature profiles have been obtained and compared with those obtained by optical interferometry. [Preview Abstract] |
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CTP.00232: A study of frequency analysis on I-V characteristic and acoustic discharge sound correlation in gliding arc discharge Ikuya Muramoto, Fumiaki Mitsugi, Tomoaki Ikegami, Yoshito Sonoda, Toshiyuki Nakamiya, Hiroharu Kawasaki, Joanna Pawlat, Henryka Danuta Stryczewska, Shin-ichi Aoqui As for atmospheric pressure electrical discharge, electric glow and arc discharge are typical. We paid attention to gliding arc discharge. We analyze I-V characteristic of gliding arc electrical discharge. We analyze the frequency of electrical discharge sound of gliding arc electrical discharge. Our purpose is to compare these two results, and to examine the relation between I-V characteristic and sound of electrical discharge. We have aimed at the gas resolution in futures in gliding arc electrical discharge. [Preview Abstract] |
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