Bulletin of the American Physical Society
62nd Annual Gaseous Electronics Conference
Volume 54, Number 12
Tuesday–Friday, October 20–23, 2009; Saratoga Springs, New York
Session URP: Poster Session II (4:00 - 6:00PM) |
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Room: Saratoga Springs City Center Hall D |
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URP.00001: ATOMIC AND MOLECULAR PROCESSES |
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URP.00002: Detection limit improvement for iodine Cordes-Band based hypersonic density measurements Jack Mills, Robert Balla, Lephsa Vuskovic Measurements in the wake region created by models in supersonic and hypersonic flows are required in order to understand a variety of problems in aerodynamics. In this experiment we investigated the properties of using broadband excitation, as opposed to narrowband excitation, using an ArF laser as a means for increasing the detection limit of density measurements in air. The mechanism for this involves Iodine Cordes-Band spectroscopy. Laser excitation of the Cordes bands of I$_{2}$ and the resulting emission involve a myriad of rotational, vibrational and electronic energy levels. I$_{2}$ is optically pumped to the D state where approximately 85{\%} of the emission regardless of buffer gas pressure results from D and D' transitions. In pure I$_{2}$ McLennan-band emission dominates with the peak signal near 321nm. As the air pressure increases, collisions with air transfer the population from the D to D' state where that emission produces the 340nm band. As the air pressure increases the 321nm emission is rapidly quenched and the D' emission dominates (340nm). This provides a pressure dependent signal contribution. The goal is to improve the current detection limit by an order of magnitude by using a broadband laser beam instead of the narrowband beam. This should increase the detection limit by an order of magnitude. [Preview Abstract] |
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URP.00003: Atomic Transition Probabilities for Neutral Cerium J.E. Lawler, E.A. Den Hartog, M.P. Wood, D.E. Nitz, J. Chisholm, J. Sobeck The spectra of neutral cerium (Ce I) and singly ionized cerium (Ce II) are more complex than spectra of other rare earth species. The resulting high density of lines in the visible makes Ce ideal for use in metal halide (MH) High Intensity Discharge (HID) lamps. Inclusion of cerium-iodide in a lamp dose can improve both the Color Rendering Index and luminous efficacy of a MH-HID lamp. Basic spectroscopic data including absolute atomic transition probabilities for Ce I and Ce II are needed for diagnosing and modeling these MH-HID lamps. Recent work on Ce II [1] is now being augmented with similar work on Ce I. Radiative lifetimes from laser induced fluorescence measurements [2] on neutral Ce are being combined with emission branching fractions from spectra recorded using a Fourier transform spectrometer. A total of 14 high resolution spectra are being analyzed to determine branching fractions for 2000 to 3000 lines from 153 upper levels in neutral Ce. Representative data samples and progress to date will be presented. \\[4pt] [1] J. E. Lawler, C. Sneden, J. J. Cowan, I. I. Ivans, and E. A. Den Hartog, Astrophys. J. Suppl. Ser. 182, 51-79 (2009). \\[0pt] [2] E. A. Den Hartog, K. P. Buettner, and J. E. Lawler, J. Phys. B: Atomic, Molecular {\&} Optical Physics 42, 085006 (7pp) (2009). [Preview Abstract] |
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URP.00004: ELECTRON AND PHOTON COLLISIONS WITH ATOMS AND MOLECULES |
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URP.00005: The field effect on elastic electron-ion collisions in a plasma with the presence of the external field Sang-Chul Na, Young-Dae Jung The field effects on the elastic electron-ion collision are investigated in a plasma with the presence of the external field. The eikonal method and effective interaction potential including the far-field term caused by the external field is employed to obtain the eikonal phase shift and eikonal cross section as functions of the field strength, external frequency, impact parameter, collision energy, thermal energy, and Debye length. The result shows that the effect of the external field on the eikonal cross section is given by the second-order eikonal phase. In addition, the external field effects suppress the eikonal cross section as well as eikonal phase for the elastic electron-ion collision. The eikonal phase and cross section are found to be increased with an increase of the frequency of the external field. It is also shown that the eikonal cross section increases with an increase of the thermal energy and Debye length. [Preview Abstract] |
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URP.00006: Electron-helium scattering in the presence of a laser field at moderate incident energies Bruno deHarak, Luis Ladino, Nicholas Martin We have begun to perform a series of experiments that examine electron-helium scattering in the presence of an Nd:YAG laser field. The goal of these experiments is to span the range of incident electron energies from 50~eV to 250~eV, and compare the results to Kroll-Watson approximation\footnote{N. M. Kroll and K. M. Watson, Phys. Rev. A 8, 804 (1973)} (KWA) calculations. Effects of an intense laser field on the elastic scattering of electrons from argon were first reported by Andrick in 1976.\footnote{D. Andrick and L. Langhans, J. Phys. B 9, L459 (1976)} In general, KWA calculations have been adequate to describe experimental results where the photon energy is significantly less than the incident electron energy -- a major exception being the case of small scattering angles where large discrepencies have been noted.\footnote{e.g., B. Wallbank and J. K. Holmes, Phys. Rev. A 48, R2515 (1973)} Our experiments will test the KWA over a range of electron incident energies that has not been previously investigated. [Preview Abstract] |
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URP.00007: A Particle-in-Cell - Monte Carlo Collision (PIC-MCC) Model for Simulations of Electron Impact Collisions in Gas Mixtures Sudhakar Mahalingam, Yongjun Choi, Seth Veitzer, Peter Stoltz A PIC-MCC model has been developed to numerically model electron impact collisions with neutral gases. This model includes elastic collisions (such as scattering, and large-angle scattering), inelastic collisions (such as excitation, and ionization) and Bremsstrahlung collisions. Collision cross sections data are based on the Evaluated Electron Data Library (EEDL) dataset, obtained from the International Atomic Energy Agency Nuclear Data Services. The EEDL library contains collision cross sections and generation data for electrons and photons for atoms with Z = 1 - 100 for incident electron energies from 10 eV (or threshold) to 100 GeV. Additionally, we have included elastic scattering cross section for electron energies below 10 eV from other experiments so that the PIC-MCC model can be used for studying low temperature plasmas. Researchers may also specify a user-defined model of cross sections to match their own measurements. We will show results for gases and parameters relevant to the plasma processes in Hall thruster applications. [Preview Abstract] |
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URP.00008: Creation, destruction, and transfer of atomic multipole moments by electron scattering: Quantum mechanical treatment Dmitry Fursa, Igor Bray, George Csanak, David Kilcrease The rates for the creation, destruction, and transfer of atomic multipole moments by heavy-particle scattering have been studied for many years using semiclassical scattering theory along with the straight-line trajectory assumption for the scattering particle and using the multitrajectory semi-classical approximation. With the advent of plasma polarization spectroscopy the same rate-coefficients became of interest for electronic collisions also in order to model the anisotropic plasmas. In this work we give general definitions for both elastic and inelastic scattering for the creation, destruction, and transfer cross sections of atomic multipole moments via the use of pure quantum-mechanical methods with due consideration for electron-exchange and for semi-relativistic effects. In order to illustrate the order of magnitude, the sign, and the energy-dependence of these cross sections we have calculated them for electron scattering from hydrogen and barium atoms using the Convergent Close-Coupling (CCC) method. [Preview Abstract] |
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URP.00009: Transport Coefficients and Cross Section Set for Electron Scattering in Mixtures CF$_4$, Ar and O$_2$ Zeljka Nikitovi\'c, Vladimir Stojanovi\'c, Zoran Petrovi\'c We present transport coefficients for electrons in mixtures of CF4 with Ar and O2 for ratios of the electric field to the gas number density E/N from 1 Td to 1000 Td (1Td=10-21 Vm2). We then add a certain percentage of radicals produced by dissociation of CF4. Our analysis of non-conservative collisions revealed a range of E/N where electron attachment introduced by radicals significantly changes electron kinetics obtained for mixtures without dissociation of CF4 gas. Results are obtained by using a simple, two term solutions for Boltzmann's equation but are verified by Monte Carlo simulations. [Preview Abstract] |
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URP.00010: DISTRIBUTION FUNCTIONS AND TRANSPORT COEFFICIENTS FOR ELECTRONS AND IONS |
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URP.00011: How valid is the concept of a bi-Maxwellian distribution? N.S. Braithwaite, R.N. Franklin The sheath of a plasma with two distinct negative species was examined by Braithwaite and Allen (1988). There is no doubt of its validity to describe the situation in electronegative plasmas at low pressures when the species are electrons and negative ions, and much of the understanding of such plasmas has resulted. Though it may be convenient to describe the electron energy distribution in electropositive plasmas as if there are two distinct species, one needs to be careful in deriving such things as a modified Bohm criterion. In most situations there is but one distribution and one cannot distinguish ``red'' and ``blue'' electrons. The electrons move between different parts of the distribution by a process of ``diffusion'' well described by Tsendin (2009). Thus unless different parts of the total electron distribution clearly do not interact, results obtained by assuming two independent populations with different densities and temperatures lack validity. [Preview Abstract] |
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URP.00012: Non-conservative charged particle swarms in ac electric and magnetic fields Sasa Dujko, Ronald White, Zoran Petrovic A time-dependent multi term solution of the Boltzmann equation has been developed and used to calculate the transport properties of charged particle swarms under the influence of time-dependent electric and magnetic fields crossed at arbitrary angle. The hierarchy resulting from a spherical harmonic decomposition of the Boltzmann equation in the hydrodynamic regime is solved numerically by representing the speed dependence of the phase-space distribution function in terms of an expansion in Sonine polynomials about a Maxwellian distribution at internaly determined temperature. The investigation is carried out over a wide range of electric and magnetic field amplitudes, field frequencies, field orientations and phases between the fields corresponding to various conditions operative in ICP. Values of mean energy, drift velocity, diffusion tensor and power density absorbed by the electron swarm for certain model and real gases are reported here. A multitude of new kinetic phenomena induced by temporal non-locality of electron kinetics were observed and explained using a physical arguments. Of special note are the phenomena associated with the synergism of magnetic field and non-conservatibve collisions. We believe that modelling of ICP and magnetically enhanced/assisted plasma reactors can greatly benefit from this study. [Preview Abstract] |
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URP.00013: IONIZATION OF ATOMS AND MOLECULES |
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URP.00014: Determination of ionization cross sections and rate coefficients for C60 by electron impact Satyendra Pal, Anshu, Neeraj Kumar, Keshav Kumar The modified semiempirical formulation for the calculations for the partial ionization cross sections of molecules by electron impact has been extended and generalized to the calculations of the cross sections for the dissociative ionization of fullerene C60. The secondary electron energy and angle dependent cross sections for the production of various dissociative ions C+60-2n (n=1-8) in electron dissociation of C60 are evaluated at fixed incident electron energies of 100 and 200eV. The integral partial ionization cross sections and their weighted sum i.e. total cross sections in the energy range varying from ionization threshold to 1000eV are also evaluated. The counting/total ionization cross sections along with the partial dissociative ionization cross sections are found in satisfactory agreement (within the composite error bars) with the available experimental data. The ionization rate coefficients at a function of energy are also derived using the present calculations for ionization cross sections and the Boltzmann distribution function of energy of the electron. [Preview Abstract] |
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URP.00015: Analytical fits for electron impact ionization cross section of atomic species commonly found in material processing plasmas A. Samolov, A. Godunov The field of plasma modeling is in need of reliable electron impact ionization cross sections. This work aims to provide accurate analytical fits for the most common atomic species found in material processing plasmas, such as Argon and halogen elements like Fluorine and Chlorine, etc. The standard BELI formula is revisited but a few other analytical expressions are also suggested, approximating single-ionization cross sections. The preference is given to experimental data up to date covering the whole range in energies. [Preview Abstract] |
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URP.00016: Fully Differential Cross Sections for Electron Impact Ionization of Formic Acid Ola Al-Hagan, Don Madison, Birgit Lohmann, Christopher Colyer, Chuangang Ning Our recent study using the molecular three-body distorted-wave (M3DW) approximation method yielded good agreement with experimental measurements for fully differential cross sections (FDCS) for the ionization of both H2 and N2 by electron impact .We will present M3DW FDCS calculations for electron impact ionization of formic acid for different energies in the coplanar geometry. Theoretical results will be compared with recent unpublished measurements for formic acid from the University of Adelaide in Australia. [Preview Abstract] |
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URP.00017: Comparison between Experiment and Theoretical Results for (e, 2e) Ionization of the 3$\sigma _{g}$ State of N$_{2}$ Ola Al-Hagan, Don Madison, Leigh Hargreaves, Christopher Colyer, Birgit Lohmann, Chuangang Ning A comparison between experimental and theoretical results for (e, 2e) ionization of the 3$\sigma _{g}$ state of N$_{2}$ will be presented. The theory presented here is the molecular three-body distorted wave (M3DW) approximation using better wave function for the molecules than we had in previous works. Results will be shown in coplanar symmetric and coplanar asymmetric geometries. We found improved agreement with experimental data using the new wave function. N$_{2}$ measurements are of particular interest due to the possibility of observing the effects of 2-center Young's-type interference terms in the cross sections. The existing experimental data suggests an interference peak but is inconclusive. [Preview Abstract] |
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URP.00018: Single Ionization of Molecular Hydrogen by 75 keV Proton Impact K. Egodapitiya, A. LaForge, J. Alexander, M. Schulz, A. Hasan, M. Ciappini, M. Khakoo Triply differential cross sections (DDCS) for single ionization of molecular hydrogen by 75keV proton impact have been measured and calculated as a function of the projectile scattering angle, energy loss, and longitudinal recoil momentum. Earlier, we reported interference structures in the DDCS resulting from coherent diffraction of the incoming projectile wave from the two atomic centers in the molecule. In the experimental data these structures disappeared near v$_{el \approx}$v$_{proj}$. It seems plausible that this disappearance may be caused by the PCI, which is known to maximize at v$_{el \approx }$v$_{proj}$. In order to test this hypothesis we have measured the recoil-ion momenta in addition to the projectile momenta in a kinematically complete experiment. Indeed, in the TDCS a weak interference structure is recovered if large longitudinal recoil-ion momenta p$^{rec}_{z}$ are selected, which kinematically suppress PCI. In contrast, for small p$^{rec}_{z}$, which kinematically favor PCI, no structure is observed. [Preview Abstract] |
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URP.00019: Cross-Sections and Fragmentation Pathways of Dissociative Electron Impact Ionization of 2,5-Dimethylfuran (C$_{6}$H$_{8}$O) C.Q. Jiao, A. Garscadden, S.F. Adams The possibilities offered by nonequilibrium plasma to guide parameters such as the mean electron energy provides researchers with an opportunity to change the energy branching in molecular gas plasmas from mainly gas heating and vibrational excitation to high-energy electronic excitation and ionization. The kinetics of the dissociative electron impact ionization of fuel molecules and subsequent ion-molecule reactions are important basic data needed for modeling the charged particle chemistries in plasmas. This paper presents the results of a high resolution Fourier-Transform mass spectrometry study on the electron impact ionization of 2,5-dimethylfuran (C$_{6}$H$_{8}$O), which is an important fuel additive and a possible renewable liquid fuel for the future. The total and partial ionization cross sections will be provided and the pathways of fragmentation channels forming major product ions will be discussed. [Preview Abstract] |
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URP.00020: Density functional theory calculation of ionization in antiproton-helium collisions Tom Kirchner, Nils Henkel, Matthias Keim, Hans J\"urgen L\"udde Probabilities and total cross sections for ionization in antiproton-helium collisions are calculated in a time-dependent density functional theory approach. The Kohn-Sham potential is approximated as the sum of the Hartree-exchange potential and a correlation potential that was proposed in the context of laser-induced double ionization. Furthermore, some approaches to the problem of calculating the ionization probabilities from the density are investigated. We find that the correlation potential yields no obvious improvement of the results over the exchange-only approximation where the correlation potential is neglected. Furthermore, we find the problem of calculating the desired observables crucial, introducing errors of at least the same order of magnitude as the correlation potential. At small energies we find that trajectory effects play an important role: the ionization cross sections are enlarged significantly if curved instead of straight-line trajectories are used to describe the projectile motion. [Preview Abstract] |
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URP.00021: OTHER ATOMIC AND MOLECULAR COLLISION PHENOMENA |
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URP.00022: Determination of collisional quenching rate coefficients of metastable nitrogen molecules by air pollutants Susumu Suzuki, Haruo Itoh It has already been investigated on the determination of the collisional quenching rate coefficients of the metastable nitrogen molecules $N_2 (A^3\Sigma _u^+ )$ by some air pollutants [1] in our laboratory. In this report, we present the result on the collisional quenching rate coefficient of $N_2 (A^3\Sigma _u^+ )$ by formaldehyde (CH$_{2}$O) using a theoretical procedure that takes into account the reflection of metastables at the boundary. As far as we know, this report is the first result of the collisional quenching rate coefficients of $N_2 (A^3\Sigma _u^+ )$ by CH$_{2}$O. Formaldehyde is a colorless gas with the foul odor, and elements of the adhesive, paints, and preservative, etc. It is widely used for construction materials such as houses, because it is low cost. It is released from paint of construction materials in air, and, in that case, it is known as one of the causative agents of so-called ``Sick building syndrome'' to influence the human body harmfully even if it is a low concentration. The obtained collisional quenching rate coefficient of $N_2 (A^3\Sigma _u^+ )$ by CH$_{2}$O is (4.7$\pm$0.4) $\times$ 10$^{-12}$ cm$^{3}$/s. Because the collisional quenching rate coefficient by CH$_{2}$O is large, it is understood that CH$_{2}$O receives energy easily from $N_2 (A^3\Sigma _u^+ )$. In addition, we reports on the obtained collisional quenching rate coefficient of $N_2 (A^3\Sigma _u^+ )$ by some air pollutants. [1] S. Suzuki, T.Suzuki and H.Itoh: Proc. of XXVIII ICPIG (Prague, Czech Republic), (2007) 1P01-40. [Preview Abstract] |
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URP.00023: PLASMA-SURFACE INTERACTIONS |
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URP.00024: A role of low pressure plasma discharge on etch rate of SiO$_2$ dummy wafer Vladimir Milosavljevic, Andrjana Zekic, Dusan Popovic, Niall Macgearailt, Stephen Daniels Plasma has become indispensable for advanced materials processing, also low--k materials as SiO$_2$ play important role in semiconductor industry. In this work a treatment of SiO$_2$ single crystal by DC plasma discharge is studied in details. There are many effects occurred during plasma--surface interactions. Our work is focused on interaction between ions and dielectric surface. The etch rates, surface morphology and chemical composition of modified surface layer obtained by DC plasma etching are reported. Influence of plasma chemistry (SF$_6$, O$_2$, N$_2$, Ar and He), discharge voltage (up to 1.2 kV), gas flow (up to 25 sccm, for each gas) and electrode--wafer geometry on etch rate of SiO$_2$ wafer have been studied. Offline metrology is conducted for SiO$_2$ wafer by SEM/EDAX technique and Raman scattering. Broad Raman peak at around 2800 cm$^{-1}$ is observed for both, treated and original, investigated SiO$_2$ wafers. Effects of plasma treatment conditions on integrated intensity of this peak are reported in the paper. An analysis of this correlation could be a framework for creating virtual etches rate sensors, which might be of importance in managing of plasma etching processes. [Preview Abstract] |
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URP.00025: Manipulation of Bias Voltage Waveform to Control Bombarding Ion Energy Distribution X. Victor Qin, Yuk-Hong Ting, Amy Wendt In materials processing applications using low pressure plasmas, positive ions are accelerated by a sheath electric field toward the substrate, where they enhance surface reactions. The amplitude of a sinusoidal bias voltage waveform applied to the substrate electrode is often used to coarsely control the average energy of bombarding ions, but generally produces a broad bimodal ion energy distribution (IED). Manipulation of the bias voltage waveform shape to produce IEDs with one or two peaks at selected energies has been previously utilized to highlight the significant role of the IED in plasma etching. Presented here are direct IED measurements made with a retarding field energy analyzer at the biased electrode. Measurements in a 10 mTorr helicon argon plasma in which ion flux and ion energy at the substrate are independently controlled clearly demonstrate the ability to predictably produce arbitrary IEDs at the substrate by tailoring the shape of the bias voltage waveform. Results for sinusoidal (500 kHz-10 MHz) and tailored (500 kHz) waveforms compare favorably with predictions based on computation of ion trajectories through the sheath electric field. [Preview Abstract] |
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URP.00026: Plasma Assisted Electron Beam Energy Boosting by Ambient Gas Pressure Optimization in Pyroelectric Crystal Accelerators James Brownridge, Stephen Shafroth Pyroelectric crystal x-ray generators [1] were first reported in 1992. These crystals have a nonzero spontaneous polarization at all temperatures below their Curie temperature. A change in crystal temperature will result in a strong electric field at its surface. If the Z- face on a Z-cut pyroelectric crystal is located in a gas at mTorr pressure the energy of electrons that are accelerated away from the crystal as it is cooled can be increased by increasing the gas pressure. As the crystal is cooled the spontaneous polarization increases, this results in an increase in the uncompensated negative charge at the surface of the crystal. The field produced by this charge is strong enough to field ionize molecules of the gas. A tentative explanation for the energy boosting of the beam follows: In this strong field these molecular ions are polarized and attracted to and stick to the surface of the crystal. Once attached to the surface of the crystal the electron cloud around the molecules is further distorted and pushed away. These polarized molecular ions increase the strength of the electric field at the surface of the crystal and increase the electron beam energy. Hence an increase in pressure boosts the beam energy. In an ultra high vacuum no energy boosting occurs. \\[0pt] [1] J.D. Brownridge, Nature (London) \textbf{358,278 (1992)} [Preview Abstract] |
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URP.00027: Cold-atmospheric pressure plasma polymerization of acetylene on wood flour for improved wood plastics composites William Lekobou, Patrick Pedrow, Karl Englund, Marie-Pierre Laborie Plastic composites have become a large class of construction material for exterior applications. One of the main disadvantages of wood plastic composites resides in the weak adhesion between the polar and hydrophilic surface of wood and the non-polar and hydrophobic polyolefin matrix, hindering the dispersion of the flour in the polymer matrix. To improve interfacial compatibility wood flour can be pretreated with environmentally friendly methods such as cold-atmospheric pressure plasma. The objective of this work is therefore to evaluate the potential of plasma polymerization of acetylene on wood flour to improve the compatibility with polyolefins. This presentation will describe the reactor design used to modify wood flour using acetylene plasma polymerization. The optimum conditions for plasma polymerization on wood particles will also be presented. Finally preliminary results on the wood flour surface properties and use in wood plastic composites will be discussed. [Preview Abstract] |
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URP.00028: Evidence of production/losses of NO on a pyrex surface under and after plasma exposure. Daniil Marinov, Olivier Guaitella, Yury Ionikh, Antoine Rousseau Molecules production on plasma exposed surfaces is of great interest for plasma/catalyst coupling used in air treatment. Interaction of real surfaces with reactive plasmas is barely studied and surface-produced molecules can provide a valuable fingerprint of the underlying processes (adsorption, desorption, recombination, chemical reactions). We use CCP discharge in 60 cm pyrex tube with \textit{in-situ }tunable laser diagnostics to monitor evolution of NO and NO$_{2}$. The tube surface is pre-treated using either Ar, O$_{2}$, N$_{2}$ or air plasma and then two types of experiments are performed i) molecules production in a pure O$_{2}$ plasma reacting with adsorbed species ii) the study of molecules losses/conversion on the surface by introducing a controlled amount of NO/NO$_{2}$ in the reactor. It was found that after N$_{2}$ plasma pre-treatment, pyrex surface is covered with nitrogen species that initiate NO production when exposed to O$_{2}$ plasma. Assuming these species are N atoms, their density was estimated [N$_{ads}$]=3$\cdot $10$^{13}$ cm$^{-2}$, what gives an assessment of the surface active sites density. Similarly, O$_{2}$ plasma leaves adsorbed oxygen species with [O$_{ads}$] $\approx $2$\cdot $10$^{14}$ cm$^{-2}_{. }$These species are capable of NO oxidation to NO$_{2}$ and inhibit NO$_{2}$ adsorption on pyrex (which is pronounced after N$_{2}$ and Ar plasma preparation). [Preview Abstract] |
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URP.00029: MATERIALS PROCESSING IN LOW PRESSURE PLASMAS: ETCHING, DEPOSITION, NEW MATERIALS |
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URP.00030: Effect of resist mask roughing on the etching profile of SiO$_{2}$ trench under the presence of local charging Shinpei Inagaki, Takashi Yagisawa, Toshiaki Makabe The reactive ion etching (RIE) of high-aspect ratio contact hole made of SiO$_{2}$ has been traditionally performed by fluorocarbon gas C$_{x}$F$_{y}$ diluted with Ar ($>$ 90{\%}) in a two-frequency capacitively coupled plasma (2f-CCP) reactor. The RIE proceeds under the competition among surface protection by the deposition of C$_{x}$F$_{y}$ radicals, chemical sputtering by energetic ions, and topological charging caused by the difference of velocity distribution of ions and electrons coming to the surface. In our previous work, feature profile evolution of SiO$_{2}$ trench pattern was predicted by using the level-set method considering mixing layer and C$_{x}$F$_{y}$ polymer layer on SiO$_{2}$ substrate. It is experimentally known that the roughness of the photoresist mask on SiO$_{2}$ film makes large influence on the etching profile, called ``faceting'' or ``striation'' probably due to the high-energy ion impact. In this study, we develop our feature profile model in order to investigate the relation between resist mask roughing and the feature profile of SiO$_{2}$ trench. Attention will be paid to the scattering of incident ions on the faceting structure of the resist mask and local charging as functions of the flux velocity distribution of ions and radicals. [Preview Abstract] |
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URP.00031: Plasma Etching of Cu in an Ar/Cl$_{2}$ Microwave Discharge M. Raskovic, K. Brannick, S. Popovic, L. Vuskovic Copper substrates can be used for depositing superconducting material thin films, such as Nb or Nb$_{3}$Sn, lowering the cost of cavity production for linear particle accelerators based on the superconducting radiofrequency technology. To avoid contamination and mechanical damage by environmental agents, the best would be to prepare Cu surface in the same apparatus thin film deposition is performed. Low volatility of Cu halides is main difficulty for using plasma processing techniques. Standard parallel plasma etching reactor does not achieve temperature necessary for evaporation of CuCl, the most volatile Cu halide. Therefore our approach was to use a microwave glow discharge [1], characterized with higher electron and radical density as well as higher substrate temperature comparing to standard RF system. Etching rates of 300 nm/min were reached using only 3 {\%}Vol Cl$_{2}$ reactive gas in Ar/Cl$_{2}$ mixture. Formation of CuCl during plasma etching process was monitored using emission spectroscopy techniques. Attempt to use observed CuCl rotational spectra for determining discharge gas temperature was made. Composition and morphology of Cu surface before and after exposure was investigated using scanning electron microscope.\\[0pt] [1] M. Ra\v{s}kovic, \textit{et al}., J. Vac. Sci. Technol. A 27, 301 (2009). [Preview Abstract] |
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URP.00032: Spectroscopic characterization and modeling of Ar/Cl$_{2}$ microwave glow discharge J. Upadhyay, M. Raskovic, S. Popovic, L. Vuskovic Ar/Cl$_{2}$ microwave glow discharge was applied for plasma etching of niobium, metal of choice for superconducting radiofrequency accelerator technology. Etching rates were determined for different discharge parameters and results of these experiments are published elsewhere [1]. Simultaneously, plasma emission actinometry was used to estimate the absolute densities of Cl, Cl$^{+}$ and Cl$_{2}$ in the variable plasma conditions. These results, combined with results of discharge diagnostics, were compared with results obtained trough the modeling of Ar/Cl$_{2}$ discharge. We have calculated the electron-impact ionization rates of Cl$_{2}$ and its fragments for electron energy distribution present in bulk plasma. These ionization rates will be used for modeling of plasma etching process and comparing with experimentally determined etching rates.\\[0pt] [1]. M. Ra\v{s}kovic, et al., J. Vac. Sci. Technol. A \textbf{27} (2), 301 (2009). [Preview Abstract] |
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URP.00033: Nano-block manipulation in CVD plasmas Hiroshi Miyata, Shinya Iwashita, Yasuyuki Yamada, Kazunori Koga, Masaharu Shiratani We have proposed a novel nano-system construction method using plasmas [1-3]. We have succeeded in realizing size control of nano-blocks and their rapid transport towards a substrate by using pulse discharges with amplitude modulation (AM) of the discharge voltage [1- 3]. We are developing a method for their three dimensional transport using a capacitively coupled RF discharge reactor having a grounded electrode with needles. During the period of AM nano-blocks are transported from their generated region rear the powered electrode to the top of the needle. Such three dimensional transport needs an asymmetric electric potential profile, in other words, a large voltage drop across the sheath near the powered electrode. We will report the experimental results and discuss the mechanism of the three dimensional transport.\\[4pt] [1] S. Nunomura, et al. J. Appl. Phys., 99, 083302 (2006).\\[0pt] [2] K. Koga, et al. J. Phys. D, 40, 2267 (2007).\\[0pt] [3] M. Shiratani, et al. Faraday Discuss., 138, 127 (2008). [Preview Abstract] |
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URP.00034: Sputter Yield Measurement of Ferrous Metals {\&} Alloys Kieran Denieffe, C.M.O. Mahony, P.D. Maguire, A. Baby Sputter yield measurements for bulk Co, Fe {\&} Ni are published [1]; however no values are available for ferrous metal alloys. Here we present the results of a study of the sputter yields of thin film ferromagnetic alloys CoFe {\&} NiFe. We also investigate the sputtering of polyamide, used for masking in microelectronics, but with no published sputter yields to our knowledge. We used a 13.56~MHz plasma ion source to bombard biased samples with 50 eV to 1k eV Ar$^{+}$ ions. The ion flux was measured by a Faraday cup {\&} the etch rate with a sensitive quartz crystal microbalance (QCM) modified for rf use, allowing multiple real-time measurements without breaking vacuum. The QCM was calibrated via profilometry {\&} weight loss measurements; flux values were validated using a retarding field analyzer. A mass/energy analyser was used to measure ion energy distributions, showed the FWHM spread of beam energy to be 4eV. Measurements show that although Y values {\&} threshold energies of the thin film alloys differ to those published for bulk ferrous metals, they do exhibit similar Y v ion energy trends.\\[4pt] [1] Laegreid N, Wehner G. 1961 \textit{J Appl Phys} 32 p365 [Preview Abstract] |
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URP.00035: Permeation barrier coating and plasma sterilization of PET bottles and foils Simon Steves, Michael Deilmann, Nikita Bibinov, Peter Awakowicz Modern packaging materials such as polyethylene terephthalate (PET) offer various advantages over glass or metal containers. Beside this they only offer poor barrier properties against gas permeation. Therefore, the shelf-live of packaged food is reduced. Additionally, common sterilization methods like heat, hydrogen peroxide or peracetic acid may not be applicable due to reduced heat or chemical resistance of the plastic packaging material. For the plasma sterilization and permeation barrier coating of PET bottles and foils, a microwave driven low pressure plasma reactor is developed based on a modified Plasmaline antenna. The dependencies of important plasma parameters, such as gas mixture, process pressure, power and pulse conditions on oxygen permeation through packaging foil are investigated. A residual permeation as low as $\rm{J = 1.0 \pm 0.3 cm^3m^{-2}day^{-1}bar^{-1}}$ for 60~nm thick silicon oxide ($\rm{SiO_{x}}$) coated PET foils is achieved. To discuss this residual permeation, coating defects are visualized by capacitively coupled atomic oxygen plasma etching of coated substrate. A defect density of 3000 $\rm{mm^{-2}}$ is revealed responsible for permeation. For plasma sterilization, optimized plasma parameters based on fundamental research of plasma sterilization mechanisms permit short treatment times of a few seconds. [Preview Abstract] |
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URP.00036: Initial Studies of Deep Silicon Etch Iqbal Saraf, Matthew Goeckner, Lawrence Overzet The kinetic behaviors of time-multiplexed deep silicon etch processes are being studied in an Oerlikon DSE II using SF$_{6}$, C$_{4}$F$_{8}$ and Ar gas flows. We have formed a model for the reactor that fits the overall pressure in time and provides insight into gas mixing during the cycle transitions. It allows one to predict cycle conditions that isolate the deposition and etch steps. Also the effect of the gas-line fill time and its correlation with residence time is studied. In addition, we have measured plasma characteristics using a diagnostic tool called a ``Wise probe''. Preliminary measurements of the ion current density (ICD) to the probe surface for SF$_{6}$ and C$_{4}$F$_{8}$ plasmas as a function of pressure, flow rates, power and bias power are presented and discussed. For both C$_{4}$F$_{8}$ and SF$_{6}$ plasmas the ion current density strongly depends upon the gas pressure in the range of 10 to 45 mTorr. However, the ion current density depends weakly on the ICP power at higher pressure (45mTorr) for both C$_{4}$F$_{8}$ and SF$_{6}$ plasmas. These kinetic dependencies are related to the time averaged silicon etch rate/profile, aspect ratio dependence, and photoresist selectivity in order to gain initial insights into the fundamental plasma-surface interactions controlling the etch. [Preview Abstract] |
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URP.00037: ENVIRONMENTAL APPLICATIONS |
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URP.00038: Development of a portable greenhouse gas analyzer based on Penning ionization electron spectroscopy (PIES) in a pulsed glow discharge plasma C. Mark Denning, Vadim Stepaniuk, Valery Sheverev A greenhouse gas (GHG) analyzer currently under development at Lenterra, Inc. is described which utilizes Penning ionization electron spectroscopy (PIES) in a glow discharge plasma. A population of helium metastable atoms (2$^{3}$S, 19.8 eV) is produced in a pulsed (50 $\mu $s duration, 5 kHz rep rate) glow discharge in helium/analyte gas mixtures. In the afterglow electrons are produced due to Penning ionization of GHG analyte molecules (including carbon dioxide and methane) by the helium metastables. These electrons possess energies equal to the energy stored in the helium metastable minus the ionization potential of the analyte molecule. Electron energy spectra are measured using the current-voltage characteristic obtained during the afterglow with a swept-voltage collector electrode. These spectra exhibit peaks that allow for the determination of the ionization potential of each analyte, and therefore selective gas detection. Experimental results are presented and components of the portable PIES device are described, including the glow discharge apparatus, as well as a carbon nanotube gas micro-concentrator and a micro gas chromatography column. [Preview Abstract] |
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URP.00039: Improved measurement system for surface loss rate of ozone Haruo Itoh, Susumu Suzuki, Ilko Mitokov Rusinov In this paper, we report on application of a technique for long-term monitoring of ozone density in a cylindrical vessel, filled with ozone-containing gas mixtures, by using ultraviolet photo-absorption. An experimental system has been used in order to monitor the temporal decrease of ozone concentration in a cylindrical cell based on the HgI 254 nm photo-absorption method [1-3]. It is applied to study the dependence of effective lifetimes of ozone on the wall material at various gas pressures. Instabilities in the mercury lamp intensity, however, often cause distortion of the measured decay curves. We have attempted to build a simple setup that eliminates the effect of long-term intensity drifts. It is based on light source intensity monitoring by a separate photo-detector and data correction in software. The obtained equivalent diffusion coefficient that describes the loss rate of ozone at the inner surface of the cell is 2.0$\times $10$^{-4}$ cm$^{2}$/s at 1 Torr. Further experiments are planned to measure the coefficient and clarify the mechanism of ozone effective lifetime. [1] H.Itoh, I.M.Rusinov, T.Suzuki, S.Suzuki: Ozone Science {\&} Engineering, Vol.26 (2004) 487-497. [2] H.Itoh, M.Rusinov, S.Suzuki,T.Suzuki: Plasma Processes and Polymers, No.2, (2005) 227-231. [3] K.Ban, S.Isegame, S.Suzuki, I.M.Rusinov and H.Itoh: Proc. 13th Asian Conference on Electrical Discharge (Hokkaido University, Sapporo, Japan) P-2-41 (2006). [Preview Abstract] |
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URP.00040: BIOLOGICAL AND EMERGING APPLICATIONS OF PLASMAS |
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URP.00041: Atmospheric-Pressure Cold Plasmas Used to Embed Bioactive Compounds in Matrix Material for Active Packaging of Fruits and Vegetables Sulmer Fernandez, Patrick Pedrow, Joseph Powers, Marvin Pitts Active thin film packaging is a technology with the potential to provide consumers with new fruit and vegetable products-if the film can be applied without deactivating bioactive compounds.Atmospheric pressure cold plasma (APCP) processing can be used to activate monomer with concomitant deposition of an organic plasma polymerized matrix material and to immobilize a bioactive compound all at or below room temperature.Aims of this work include: 1) immobilize an antimicrobial in the matrix; 2) determine if the antimicrobial retains its functionality and 3) optimize the reactor design.The plasma zone will be obtained by increasing the voltage on an electrode structure until the electric field in the feed material (argon + monomer) yields electron avalanches. Results will be described using Red Delicious apples.Prospective matrix precursors are vanillin and cinnamic acid.A prospective bioactive compound is benzoic acid. [Preview Abstract] |
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URP.00042: Plasma needle treatment of bacteria known to cause infections of the soft tissue of the oral region and bones Dejan Maletic, Sasa Lazovic, Nevena Puac, Gordana Malovic, Zoran Lj. Petrovic, Maja P. Miletic, Dusan B. Pavlica, Milena Z. Jovanovic, Pavle Milenkovic Plasma needle can be used for non-contact disinfection of dental cavities and wounds, minimum-destructive precise treatment, as well as the removal of damaged tissue. The effect of bacterial deactivation is probably caused by reactive oxygen species while nitric oxide provided by plasma plays major role in many processes in the organism. Mass spectrometry was done to provide better insight into plasma-cell interactions. Our measurements were performed on a plasma needle that we originally used for the treatment of plant cells.Our research was done on species that are known to cause primary and secondary infections of the soft tissue of the oral region, as well as bones. The bacteria cultures used are bacterial reference culture species Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 25922. We investigated the effect of the plasma needle discharge on different concentration of bacteria using several exposure times and power transmitted to the plasma. It was found that excellent removal of this and other bacteria may be achieved by the plasma needle treatment. [Preview Abstract] |
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URP.00043: Modeling and experiment of ring-shaped emission profile in plasma bullet Yukinori Sakiyama, David Graves, Julien Jarrige, Mounir Laroussi Our recent measurement demonstrated that a plasma ``bullet'' at atmospheric pressure shows ring-shaped emission profile. In this study, we focus on the mechanisms of the ring-shaped profile by means of finite element method and spectroscopic measurement. Our model is based on a fluid model with the local field approximation in 1D cylindrical coordinates, corresponding to a cross section of a plasma bullet. An expected concentration gradient of humid air is assumed to be present due to diffusion of air. Pulse-like electric field is given perpendicular to the simulation domain. Our simulation results show that the major ionization reaction is Penning ionization between nitrogen (air) and helium metastables. The density of electrons and positive nitrogen ions show the peaks near the outer boundary due to the higher concentration of air there. Accordingly, the emission peak appears near the outer boundary, corresponding to a ring-shaped emission profile. Experiments were performed with a dielectric barrier discharge reactor driven by high voltage short rise time pulses. Radial profile and time-resolved OES of radiative species were compared to simulation results. [Preview Abstract] |
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URP.00044: Treatment of Second Order Structures of Protein on Medical Equipments Using Oxygen Plasma Nobuya Hayashi, Satoshi Kitazaki, Masaaki Goto, Yoshihito Yagyu, Akira Yonesu Removal of proteins from the surface of medical equipments are attempted using an RF plasma. Oxygen gas is introduced into a vacuum chamber with dimensions of 450 mm in length, 200 mm in diameter and 20L of capacity. When an RF power (13.56 MHz, 60W) is applied to an ICP type antenna, oxygen radicals (atomic oxygen and excited oxygen molecule) are produced below the antenna. The characteristics of removing protein from the medical equipments was investigated using casein and heat-resistive keratin proteins. Initial concentration of the proteins on a CaF2 substrate is several mg/cm2. The treatment effect of proteins is determined by the peak height of chemical bonds in amide and second order structures appeared on FTIR spectra. The second order structure of a protein such as alpha-helix and beta-sheet are decomposed with the treatment period. Complete treatment of proteins including the second order structure requires several hours avoiding the damage to medical equipments. [Preview Abstract] |
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URP.00045: Sterilization of Long Tube Inner Surface Using Oxygen and Water Vapor Plasmas Produced by AC HV Discharge Satoshi Kitazaki, Nobuya Hayashi Oxygen and water vapor plasmas inside a narrow long tube were produced using an AC HV glow discharge at low pressure in order to sterilize the inner surface of a tube. In order to produce plasma inside a narrow tube, an AC high voltage was adopted. The material of the tube used in this experiment was silicon rubber. The length and diameter of the tubes ranged from 300 to 1,000 mm and from 1 to 4 mm, respectively. The tube was placed in a stainless steel vacuum chamber and was evacuated to 10 Pa using a rotary pump. The material gas for plasma and radical productions was pure oxygen or water vapor, which was introduced to the chamber from a gas cylinder or water reservoir. Light emission spectral lines of oxygen and OH radicals were observed at 777 nm and 306 nm, respectively. The chemical indicator was inserted into the tube and turned to a yellowish color (from the original red) after a treatment, which indicates the generation of sufficient oxygen on OH radicals for sterilization. A tube with the length of 500 mm and diameter of 4 mm is sterilized using oxygen plasma by 10 minutes treatment. Also a tube with the length of 300 mm and diameter of 2 mm is sterilized using water vapor plasma by 5 minutes treatment. [Preview Abstract] |
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URP.00046: ABSTRACT HAS BEEN MOVED TO SR1.00005 |
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URP.00047: FTIR Analysis of Process Effluent Generated From Tissue Removed By Plasma-Chemical Process Il Gyo Koo, Myeong Choi, Cameron Moore, George Collins We present analysis of the effluent produced during a tissue removal proccess driven by a RF excited plasma which generates chemical species. We collected and analyzed the process by-product gas, small particles trapped by fine-pore filtration, and the post-process tissue surface using FTIR absorption and ATR-FTIR. From these data we make initial estimates for the kinetic pathways that are accessed by the plasma-based tissue removal process. [Preview Abstract] |
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URP.00048: Analysis of Plasma Based Tissue Removal versus Standard Electrosurgery Arlen Ward, Il Gyo Koo, Myeong Yeol Choi, George Collins This study compared and contrasted biological tissue removal via plasma chemistry compared and contrasted with standard electrosurgery. With high speed image capture of the tissue division, the mechanism differences between the two methods are evident. While standard electrosurgery removes tissues with thermal vaporization during arc events, the plasma application modifies the tissue structure during plasma exposure. The thermal damage zones in the remaining tissue are also compared between techniques. [Preview Abstract] |
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URP.00049: Comparative Histology of Plasma Treated Tissue Kyle Rick Atmospheric plasmas applied in surgical settings have unique characteristics found in histological results from animal tissue studies. This is evident in both ex vivo bench tissue tests and in vivo fresh tissue. Examples of these histological features are presented as results of a comparative study between plasma treated, common medical argon coagulation, and electrosurgery. [Preview Abstract] |
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URP.00050: Fabrication of two types of atmospheric pressure microplasma jet sources: A capillary electrode and a single pin electrode surrounded by tapered insulator with eight holes Tae Hun Chung, Sun Ja Kim, Hye Sun Park, Se Hwan Bae Atmospheric pressure microplasma jet sources driven by radio-frequency wave and by low frequency pulsed wave of several kilohertz were specially fabricated and characterized. Two different types of jet were developed. The first one consists of a sharpened metal pin which is covered with a cone type Teflon layer confined in an acrylic tube. This structure allows an efficient ignition since the electrical field is concentrated at the end of electrode. The second one is a jet with a capillary electrode in which the working gas, helium or argon, and the additive gas, oxygen, are fed into the tube. The electrical properties of the discharges have been studied by means of voltage and current probes. The neutral gas temperature and the electron temperature are measured by optical emission spectroscopy. The neutral gas temperature is compared with the results obtained by optical fiber thermometer. To study the effect of pulsed discharges, we utilized a pulsed high voltage source with the variable frequency of 10-60 kHz and the voltage of 1-10 kV$_{PP}$. The effects of various design configurations and operation parameters were investigated. The cultured mammalian cells were treated using the plasma jet sources. The effects of plasma jet treatment were observed with a special focus on the cell apoptosis. [Preview Abstract] |
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URP.00051: Absolute ozone measurements for a low-energy pulsed plasma needle Chunqi Jiang, Vincent Puech, Lionel Magne, Pascal Jeanney Applications of an atmospheric-pressure, nanosecond pulsed plasma jet for biomedical and dental disinfections have motivated numerous diagnostic studies in understanding of the underlying physics and chemistry during the plasma bactericidal processes. In this work, we present spectroscopic studies of a 3 cm long needle-like He-O$_{2}$ plasma jet. Rotational temperature of the plasma jet was measured to be about 300 K with optical emission spectroscopy. Ozone, as a typical bactericidal species, was detected in the plasma. Optical absorption spectroscopy identifies the absolute concentration ozone to be 10$^{15}$ cm$^{-3}$ when the plasma was powered with 140 ns, 6 kV pulses at 1.5 kHz. The production of ozone increases with pulse voltage and pulse repetition rate. O$_{2}$ concentration in He was also found affecting the ozone generation. In addition, two-photon laser induced fluorescence radially resolves an ozone profile in a diameter of 1 mm produced by the plasma needle. [Preview Abstract] |
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URP.00052: Study of structural modification of sugarcane bagasse employing hydrothermal treatment followed by atmospheric pressure plasmas treatment Jayr Amorim, Maria Teresa Pimenta, Leandro Gurgel, Fabio Squina, Jorge Souza-Correa, Antonio Curvelo Nowadays, the cellulosic ethanol is an important alternative way to many liquid biofuels using renewable biomass rich in polysaccharides. To be used as feedstock for ethanol production, the bagasse needs to be pretreated in order to expose its main constitutive. The present work proposes the use of different pretreatment processes to better expose the cellulose for hydrolysis and fermentation. In the present paper the sugarcane bagasse was submitted to a hydrothermal pretreatment followed by atmospheric pressure plasmas (APPs). An RF microplasma torch was employed as APPs in Ar and Ar/O$_{2}$ mixing. The bagasse was treated in discharge and post-discharge regions. The position and time of treatment was varied as well as the gas mixture. The quantity of polysaccharides was determined by using high performance liquid chromatography. It was observed the release of a fraction of the hemicelluloses in the sugarcane bagasse. Modifications in the surface of the sugarcane fibers were monitored by employing scanning electron microscopy. [Preview Abstract] |
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URP.00053: PLASMA DIAGNOSTICS: OPTICAL, ELECTRICAL, OTHERS |
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URP.00054: Diagnostic of N2(A) concentration in high velocity nitrogen afterglow at atmospheric pressure Anne-Marie Pointu, Evgeny Mintusov An optical emission diagnostic was used to measure N2(A) concentration in a high velocity (1000 cm/s) N2 flowing afterglow of corona discharge at atmospheric pressure, used for biological decontamination. Introducing impurities of NO ($<$1e-5) we used two well separated and relatively intense lines of NO gamma and beta bands (248nm and 321 nm), easily studied with a low resolution spectrometer. Based on a simplified transport kinetics, the technique is validated using a variation of lines intensity ratios used as coordinates, for numerous experimental points, measured at different axial distances and for different values of NO injected flow. Moreover, it has been demonstrated that N2(A) creation comes from N+N+N2 atom recombination with a global rate around 2e-33 cm$^{6}$/s, a result which agrees with literature, as well as N2(A) loss mechanisms were confirmed to go via quenching with O and N atoms. The order of magnitude of obtained N2(A) concentration, about 1e11 cm$^{-3}$, coincides with the results of direct measurement (by Vegard-Kaplan band), using a spectrometer of better resolution. [Preview Abstract] |
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URP.00055: Spatial variation of O$^{-}$ Energy distribution in an RF magnetron plasma H. Toyoda, K. Goto, T. Ishijima, N. Ohshima, K. Kinoshita Magnetron plasmas are one of the most important tools for sputter deposition of thin films. However, energetic particles from the sputtered target sometimes induce physical and chemical damages to the deposited film surface during the sputtering processes. For example, magnetic and/or electrical properties of magnetic recording films or magnetic tunneling junction for magnetoresistive random access memory (MRAM) are sensitively changed with sputtering condition, suggesting the damage to the deposited film interface. Therefore, measurement of energetic particles in the magnetron plasma is indispensable to improve the deposition process. So far, we have investigated behavior of high energy Ar atoms backscattered from the sputter target, using a quadrupole mass analyzer (QMA) with an energy analyzer. As another possible energetic species in magnetron plasma, oxygen negative ions in oxide targets is known and existence of O$^{-}$ ions up to a few hundred eV has been reported in YBCO magnetron sputter plasma. In this paper, energy distribution of O$^{-}$ and their spatial variation in an RF magnetron plasma is measured using a QMA with the energy analyzer. An equivalent circuit model which explains the spatial variation of O$^{-}$ energy distribution is proposed. [Preview Abstract] |
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URP.00056: Sheath Effects on Electron Density Measurements in Frequency Shift Probe and their Application to Electron Temperature Measurements Keiji Nakamura, Qi Zhang, Hideo Sugai Technologies of plasma monitoring are important for accurate plasma control. We have developed a frequency shift probe, and the probe enables us to measure an electron density from variation of resonance frequency of the probe head similarly to the hairpin probe. A plane structure of the probe head make it possible to minimizes disturbance to the processing plasma, and the probe is applicable to a reactive polymer-deposition plasmas since the polymer has no significant effects on the resonance frequency. The electron density is usually obtained from a plasma-induced shift of the probe resonance frequency, however influences of a sheath around the probe should been considered for more precise density measurements. In this work, sheath effects on the frequency shift probe were investigated, and the frequency shift probe was applied to measure a electron temperature using the sheath effects. As the sheath thickness increased, the resonance frequency decreased, and the sheath effect is enhanced depending on probe structure. Since the sheath width is proportional to Debye length, the probe resonance frequency depends on electron density and electron temperature, suggesting that resonance frequencies obtained in two probes having different sheath dependence gives an unique solution of the density and temperature of electrons. [Preview Abstract] |
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URP.00057: Electromagnetic treatment of the multipole resonance probe Martin Lapke, Thomas Mussenbrock, Ralf Peter Brinkmann We present an electromagnetic model of the ``multipole resonance probe'' (MRP)-- a diagnostic concept which enables the simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure gas discharges. The MRP is a radio-frequency driven probe of particular spherical design. In an idealized version the probe consists of two dielectrically shielded, conducting hemispheres. Driven by a radio-frequency source, the hemispheres are powered symmetrically. An analysis of the absorption spectrum shows a multitude of resonances, which allows for an analytical evaluation of the measured signal. The signal provides information on the distribution of the plasma in the probe's vicinity, from which the values of electron density, electron temperature and collision rate can be inferred. In this contribution the MRP will be modeled electromagnetically. Based on a comparision between full electromagnetic and electrostatic treatment, we show that a previously presented electrostatic treatment [1] was well justified.\\[4pt] [1] M.Lapke et al., Appl. Phys. Lett. {\bf 93}, 051502 (2008) [Preview Abstract] |
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URP.00058: Determination of Ar($3p^54s$) number densities in an inductively coupled plasma R.O. Jung, John B. Boffard, Chun C. Lin, A.E. Wendt Metastable and resonance level atoms can build to substantial number densities in laboratory plasmas and play an important role in various dynamical processes within the plasma. We have measured number densities of the four Ar($3p^54s$) levels using two independent optical techniques for a range of source pressures (1-25 mTorr) in an Ar inductively coupled plasma (ICP). In the first technique, radiation from a Xe arc lamp is passed through the plasma and the resulting (white light) absorption dips yield number densities. The second method employs a simplified radiation trapping model (based on a photon escape factor) to exploit changes in observed branching fractions of optical emissions corresponding to an array of $3p^54p \to 3p^54s$ transitions, which are sensitive to number densities of the $3p^54s$ levels via reabsorption. Results of these two methods and a related method developed by Schulze \emph{et al.}\footnote{M Schulze \emph{et al.}, J Phys. D: Appl. Phys. \textbf{41}, 065206 (2008)} are shown to be consistent, validating use of the emission technique for measuring number densities of excited species. We also present similar measurements of the four levels of the Ne($2p^53s$) configuration in a pure Ne plasma. [Preview Abstract] |
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URP.00059: OES-Measurement on the spatial distribution of the Ar(1s5) population density in a 2f-CCP Kazuki Takahashi, Tomihito Ohba, Toshiaki Makabe Capacitively coupled plasmas (CCPs) are generally used for SiO2 etching processes. The application of RF-power to both electrodes of a CCP (2f-CCP) provides advantages for the operation. Optical emission spectroscopy (OES) is widely used as noncontact method to determine plasma parameter. Ar metastables play an important role for the characteristics as a probe of active dissociated molecules (radicals). Since metastables are non-emissive species, their population density can not be directly evaluated from OES. In the present study we measured Ar(1s5) population densities by using the combinations of line intensity ratios emitted from upper states and the escape factor of radiation trapping, following Schulze et al. [J. Phys. D: 41 (2008), 065206]. Abel inversion is used to resolve the spatial distribution. Due to diffusion, the spatial distribution of the Ar metastable density is different from the density of the short-lived resonance states. We show that there exists a density of Ar(1s5) in front of the side wall as expected. We focus on the spatial distribution of the Ar(1s5) density and discuss its behavior compared with Ar(2p2). [Preview Abstract] |
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URP.00060: Optical emission spectroscopy of a dynamic E-H transition in an inductively coupled plasma in Ar Satoshi Morishita, Yuichiro Hayashi, Toshiaki Makabe Inductively coupled plasmas (ICPs) are used as a high density plasma source in various applications. It is well-known that an ICP has two operating modes, E and H mode. The transition between both modes shows strong hysteresis behaviors in various characteristics. In our series of experiments, we have studied the E-H transition in Ar for 100 and 300 mTorr in an ICP driven by a single-turn coil around a quartz tube. In our recent research we investigate the dynamic optical characteristics of the E-H transition, in the form of the integrated signal along the axial direction, by using an ICCD camera. In the present study, the net excitation rate of Ar(2p9) mainly caused by two-step collisions of electrons with energy comparable to 1.5 eV is observed. The temporal change in the transition of Ar(2p9) is compared with that of previous measured Ar(2p1) caused by electrons with energy greater than 13.6 eV. Discussion will be focused on the influence of high- and low-energy electrons on the dynamic transition. This work is partly supported by Global COE program operated in Keio University. [Preview Abstract] |
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URP.00061: Ion mass spectrometry in plasma doping system John (Bon-Woong) Koo, Ziwei Fang, Ludovic Godet, James Buff, Deven Raj, Timothy Miller Plasma doping provides cost effective dopant implantation in semiconductor device fabrication. Unlike conventional beamline implantation, plasma doping is not mass-analyzed, making control of the ion species in the low temperature plasma very important. It is also a pulsed system, making time resolution important. We report time-resolved measurements during and after the high voltage pulse in BF3 plasma. For B2H6, we report a correlation between ion mass spectrum data and processed wafer data. For AsH3, we report the ion composition changes with respect to several plasma parameters. These investigations have led to a better understanding of the gas phase phenomena, including the electron-radical interactions. [Preview Abstract] |
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URP.00062: Electron Density Measurements in a Supersonic Flowing Ar/H$_{2}$/Air Discharge M. Nikolic, D.J. Drake, P. Laurin, S. Popovic, L. Vuskovic Local measurements of the electron density in high pressure discharges have commonly been performed through use of an electrical probe, such as a Langmuir probe, or by the Stark broadening of the hydrogen lines. However in supersonic flowing discharges electrical probes can cause shocks to form, which is unwanted. In addition, these types of discharges do not often contain the hydrogen needed to determine the electron density through Stark broadening where the measurements are hampered by the lack of intensity and breadth of the hydrogen Balmer lines. An alternative approach is to use the intensity of the rotational bands of the N$_{2}$ second positive system. We performed detailed measurements of the population densities of the N$_{2}$ C$^{3}\Pi _{u}$-B$^{3}\Pi _{g}$ system and the hydrogen Balmer lines in a supersonic flow of weakly ionized Ar/H$_{2}$/Air. Gases were premixed in the stagnation chamber at room temperature by adding up to 10{\%} hydrogen and up to 45{\%} air to pure argon. A cylindrical cavity was used to sustain a discharge in the pressure range of 100-700 Pa. Absolute emission spectroscopy was used to determine the gas temperature in the flow from the N$_{2}$ system. Comparison was made between the results obtained from the N$_{2}$ band intensity technique and Stark broadening of the hydrogen Balmer lines. [Preview Abstract] |
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URP.00063: On the floating harmonics method in non-Maxwellian plasmas Aram Kim, Jin Young Bang, Chin Wook Chung The floating harmonics method applicable to measure electron temperature and ion density in processing plasmas assumes that electrons are in a Maxwellian distribution [1]. To investigate the effect of non-Maxwellian electron distributions to the floating harmonics method, the electron energy distribution functions (EEDFs) were measured. The electron temperatures from the EEDFs at floating potentials were compared with that from the floating harmonics method. Slight discrepancies between them were observed. A new approach to address this was proposed using the second harmonics and third harmonics of the probe current and was compared. This method was not affected by the displacement current due to the stray capacitance of the measure system. The results were in good agreegment with the electron temperature from the EEDFs at floating potentials. \\[4pt] [1] M. H. Lee, S. H. Jang and C. W. Chung, J. Appl. Phys., 101, 033305 (2007) [Preview Abstract] |
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URP.00064: Spectroscopic studies of the primary-to-secondary streamer transition in short air gap Yuri Shcherbakov, Leonid Nekhamkin, Reidar Sigmond We present results on synchronous spectroscopic and electrical studies of the filamentary streamer discharge in short air gap in stage of primary-to-secondary streamer transition. This study continues our previous studies of the high-stable DC positive streamer corona by measurement of absolute intensities of the second positive (SPS) and first negative (FNS) systems of molecular nitrogen. Special attention was paid to measurement of the luminosity intensities just at the moment of arrival of the primary streamer at the cathode followed by the stage of very fast redistribution of the electric field as well as by the stage of the relatively low-speed neutralization of the primary streamer channel to transform finally to the secondary streamer in resistive stage of the residual streamer channel. Spectroscopic data have been supplemented with synchronous electric current waveforms. Some preliminary theoretical analysis has been done for the very fast stages of streamer dynamics near the cathode. [Preview Abstract] |
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URP.00065: Real time two-dimensional spatial distribution measurement method of electron temperature and plasma density Young Cheol Kim, Sung Ho Jang, Gun Ho Kim, Chin Wook Chung Real time two-dimensional spatial distribution measurement method of electron temperature and plasma density was developed. It is based on a floating probe method [1] because the floating probe has high time resolution. Two-dimensional array of sensors on a 300 mm diameter wafer-shaped printed circuit board (PCB) and a high speed multiplexer circuit were used for real time distribution measurement. The method was tested at various powers and pressures, spatial distributions of the electron temperature and the plasma density could be obtained. And in the measurement results, asymmetric plasma density distributions caused by pumping port effect could be observed. This method can measure spatial distribution of plasma parameters on the wafer in real time without plasma perturbation, therefore it will be expected to improve the uniformity of processing plasmas such as etching and deposition. \\[4pt] [1] M. H. Lee, S. H. Jang, C. W. Chung, J. Appl. Phys. 101, 033305 (2007). [Preview Abstract] |
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URP.00066: Measurements of electron energy distributions in short DC discharges J.M. Williamson, S.F. Adams, J. Blessington, V.I. Demidov The energetic portion of the electron energy distribution function (EEDF) in short DC discharge plasmas was investigated. For this experiment, a short DC discharge with a conducting radial wall and cold cathode was used. The conducting wall was electrically isolated and used as a large electric probe. The probe surface area was much larger than a typical cylindrical Langmuir probe. The application of the wall as an electric probe for plasma measurements was possible under the condition of nonlocality of the EEDF. Nonlocality is related to the dimension of the plasma volume and the gas pressure. Increasing the probe surface area results in an increase in probe sensitivity. Since the wall probe was nearly flat, the resulting contribution of the ion current to the measurements was also dramatically reduced. The measured EEDFs had clear signatures of the creation of energetic electrons in the plasma from atomic and molecular volume processes. Plasma particle densities were estimated from the probe measurement. [Preview Abstract] |
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URP.00067: ABSTRACT WITHDRAWN |
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URP.00068: ABSTRACT WITHDRAWN |
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URP.00069: Retarding field analysis of the time resolved ion energy distribution at a biased electrode David Gahan, Borislav Dolinaj, Mike Hopkins Retarding field energy analyzers (RFEAs) are commonly used to measure the ion energy distribution function (IEDF) at grounded and driven electrodes in plasma reactors. At the grounded surface the RFEA operation is easier to implement due to the absence of large voltages. At the driven electrode the RFEA design is more complex. Filtering techniques are used to ensure the entire RFEA floats at the electrode bias potential. If the discharge, or the substrate electrode, is driven with a pulsed signal the time resolved IEDFs through the pulse cycle are desirable. RFEAs and mass spectrometers have been used to make time resolved measurements of the IEDF at grounded surfaces in discharges pulsed in the tens/hundreds of kHz range. Time resolved measurements made at a pulsed bias surface are more complicated, mainly because of the need to incorporate low pass filters to allow the RFEA to float at the bias potential. Here, we present time resolved IEDF measurements at a pulsed/rf driven electrode in the kHz range. The RFEA body is allowed to float at the bias potential while the internal components are rf grounded. The ion retarding potential is always determined relative to the instantaneous RFEA body potential. Time resolved IEDFs are presented for various square pulse and sinusoidal bias waveforms. [Preview Abstract] |
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URP.00070: Electrical and emission spectroscopic investigation of a self-pulsing micro hollow cathode discharge Beilei Du, Sebastian Mohr, Dirk Luggenhoelscher, Uwe Czarnetzki Micro hollow cathode discharges (MHCD) consist of two electrodes separated by a thin dielectric (here: 100 $\mu $m). The discharge develops in a hole penetrating all three foils (200 $\mu $m diameter). When powered by a DC voltage of several 100 V, the discharge shows self-pulsing operation. Voltage and current measurements, optical emission measurements by an ICCD camera equipped with a microscope lens as well as the determination of electron density from the Stark broadening of the H$_{\beta }$-line are performed in argon at pressure from several 1000 Pa to atmospheric pressure. The voltage-current characteristic during self-pulsing indicates a transition from abnormal mode to spark mode as in a DC glow discharge. The pulse frequency can range from kHz up to about 1 MHz and depends on the capacitance of the discharge setup. The pulse width can be as short as several 10 ns and the current peaks can be as high as 1 A. With the appearance of the self-pulsing the electron density increases from the order of 10$^{15}$ cm$^{-3}$ during the non self-pulsing operation to the order of 10$^{16}$ cm$^{-3}$. A comparison of the plasma conductivity obtained from the performed measurements with the electrical measurements shows excellent quantitative agreement. [Preview Abstract] |
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URP.00071: X-Ray Induced Breakdown in Air at High Reduced Electric Field: Experimental Details Robert Vidmar, Anusha Uppaluri Breakdown of laboratory air in parallel plate geometry was triggered by an X-ray pulse originating from an electron beam source. The electron beam operates at 100 keV and a few mA for a few hundred ns to several ms. The source is shielded with stainless steel and lead from the breakdown n device. Theory is presented relating the X-ray count rate in a NaI(Tl) crystal to the volumetric ionization rate in air. Measurements quantify the X-ray count rate in a detector and provide an estimate of the volumetric ionization rate during an X-ray pulse. An air-chemistry code provides a time history of electrons and air species leading up to breakdown in air subject to high reduced electric field. Measurements are made with a parallel plate geometry biased to near breakdown. X-ray emissions serve as the source of ionization resulting in breakdown. Details of the method and measurements are discussed. [Preview Abstract] |
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URP.00072: RF Measurement Techniques and Improvements Carl Almgren, Scott Heres, Cameron Moore, George Collins Measurements of RF voltage, current, and phase at the plasma load (after the matching network) requires a careful implementation, especially for plasmas at atmospheric pressure with small electrode surface areas and excitation volumes. We present a comparison of measurements produced by two commercial instruments and conclude that to achieve accuracy with minimal perturbation requires an understanding of the equivalent circuit for the sensing method used. Finally we discuss how impedance match characteristics and a chosen measurement method need both be considered as a system when making these measurements. [Preview Abstract] |
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URP.00073: Modeling of Optical Emission Spectra in an Ar Pulsed Discharge to Determine Absolute Metastable Density S.F. Adams, J.A. Miles, A.C. Laber, J.M. Williamson Optical emission measurements of relative intensities of violet spectral lines in an Ar pulsed discharge have been combined with available electron-impact cross sections to yield absolute Ar metastable species concentration. An enabling factor of this analysis is that the electron excitation pattern from the Ar singlet ground state and the triplet metastable state (1s in Paschen's notation) is quite different between the 10 levels of the resonant 3p state (3p$_{1}$..3p$_{10})$. The result of this pattern is that the emission spectrum of 3p-1s transitions will display a unique intensity distribution depending on whether the 3p state is generated by direct excitation from the ground state, or by stepwise excitation from one of the 1s metastable states. Data is shown for a model that accurately simulated experimental spectra using the metastable state density and the E/N as fitting parameters. [Preview Abstract] |
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URP.00074: High accuracy identification of microwave hairpin resonances Mark Bowden, Vladimir Samara, Nicholas Braithwaite The quarter-wave hairpin resonator is a useful density diagnostic in low pressure plasmas. Among its advantages are the immediacy and potential accuracy of the determination of electron density by a microwave frequency measurement. One difficulty in making high precision measurements has been the identification of the precise resonant frequency because of the shape of the resonance and the background signal on which it is superimposed. In a development of the hairpin method the mean potential of the hairpin is directly modulated at a few kHz while a separate, inductively coupled microwave signal is swept through the range of resonance. When immersed in a plasma the low frequency modulation perturbs the electron density in the immediate vicinity of the hairpin, impressing a modulation on the resonant frequency. At resonance there is a sharp phase change in the modulated microwave reflection (referenced to the modulation input). This aids identification of the resonance since all other structure in the microwave signal reflected from the hairpin is unaffected. This provides a simple determination of the resonance that can be readily implemented in software for automated measurements, with time resolution restricted only by the modulation period. The method has been demonstrated in a GEC reference cell with pulsed and steady CCP excitation at 13.56 MHz. [Preview Abstract] |
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URP.00075: The electron temperature measurement by using an optical emission spectroscopy in inductive Ar/O2 mixture discharge Yu Sin Kim, Young-Kwang Lee, Chin-Wook Chung Electron temperatures (Te) were measured by using an optical emission spectrometer (OES) method in Ar/O2 mixture inductively coupled plasma. The OES method is based on the simple collisional-radiative model with relative intensities from the light emission of the argon 4p level [1]. The OES measurements were compared with the floating harmonics method [2]. At a pure argon discharge of 5 mTorr, the measured Te from the OES method was 3.6 eV. As O2 flow rates increase, the Te increased gradually from 4.1 eV to 4.7 eV. However, the Te from the OES method was slightly higher than that of the floating harmonics method. These differences caused by changed metastable densities which can affect the light intensity ratio of the 4p lines and the error of rate coefficient(K) values. Although there are a little difference of the Te, note that trends of the measured Te with the O2 addition were good agreement with that from the floating harmonics method. These results show that our OES method is applicable to the plasma diagnostics in the mixture gas discharges such as an industrial plasma process monitoring because this noninvasive OES method does not perturb the plasmas. [1] Y.K. Lee, K.T. Hwang, M.H. Lee and C.W. Chung, J. Korean Phys. Soc. 52. 6(2008) [2] M.H. Lee, S.H Jang, and C.W. Chung, J. Appl. Phys. 101, 033305 (2007) [Preview Abstract] |
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URP.00076: Simple in situ method for real time measurement of dielectric film thickness in plasmas Sung-Ho Jang, Gun-Ho Kim, Chin-Wook Chung An in situ thickness measurement method of dielectric films (Dual frequency method) was developed, and the thickness was measured in an inductively coupled plasma. This method uses a small AC bias voltage which has two frequencies for the thickness measurement. The dielectric thickness is obtained from measuring amplitudes of two frequency ac current through a sensor and using an equivalent circuit model describing impedance of the dielectric film and the plasma sheath. In the experiment, thicknesses of Al$_{2}$O$_{3}$ film could be accurately measured in real time. To check the measurement reliability, the dual frequency method was compared with Reflection spectrophotometry as a kind of optical thickness diagnostics, and it was found that the dual frequency method agrees closely with reflection Spectrophotometry at various rf powers and pressures. In addition, this method is very simple and able to install at anywhere in plasma reactors in contrasted with optical methods, therefore it is expected to be applied to in situ surface diagnostics for various processing plasmas. [Preview Abstract] |
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URP.00077: Rotational CARS Temperature Measurements in Nanosecond Pulse Discharge Plasmas Yvette Zuzeek, Keisuke Takashima, Igor Adamovich, Walter Lempert Time-resolved and spatially resolved temperatures in repetitively pulsed nanosecond discharges in air and ethylene-air mixtures have been measured by purely rotational Coherent Anti-Stokes Raman Specroscopy (CARS). The experiments have been done in a capacitively coupled plane-to-plane discharge and in an atmospheric pressure near-surface Dielectric Barrier Discharge (DBD), both powered by repetitive nanosecond duration voltage pulses. Gated ICCD camera images demonstrated that the capacitively coupled discharge plasma remains diffuse and stable, with no sign of arc filaments. Comparison of the experimental results with plasma chemical kinetic modeling calculations shows good agreement. The results demonstrate that the rate of heating in the fuel-air plasma is significantly more rapid compared to the one in the air plasma. Kinetic model analysis shows that this occurs due to exothermic reactions of fuel with radical species generated in the plasma, such as O atoms. The present results provide additional insight into kinetics of hydrocarbon fuel oxidation in low-temperature plasmas and into the mechanism of localized heating of air flows by nanosecond DBD discharges. [Preview Abstract] |
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URP.00078: Properties of a hairpin probe in a strongly magnetized plasma S.K. Karkari, G.S. Gogna, D. Boilson Understanding of the physics in the filter field region of a neutral beam injection source for ITER under development is very important, as this region is where the negative ions are generated and extracted. For accurately determining electron densities in this complex plasma, a floating hairpin probe is applied on the KAMABOKO III ion source, at the MANTIS test bed at CEA Cadarache. The technique is based on measuring the probes resonance frequency (few GHz) shift in plasma with respect to that obtained in vacuum. The resonance frequency is proportional to the permittivity of the medium filling the space between the wires of the hairpin resonator. Using this technique we obtained the electron density variation as function of discharge power and on the external grid bias in front of the plasma grid. [Preview Abstract] |
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URP.00079: PLASMA CHEMISTRY: ATMOSPHERIC, GAS PHASE, SURFACE |
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URP.00080: Developing a Consistent Chemical Kinetic Model for Electron Beam Irradiation of Humid Air Theodore Dibble, Karen Schmitt, David-Anthony Murray A chemical kinetic model has been assembled to assist in better understanding the mechanisms underlying hydroxyl radical production via electron beam irradiation of humid air. Thermodynamic determination of the feasibility of particular product sets was used to eliminate certain reactions proposed previously, dynamical models were used to guide the choice of product sets, and updated rate constants were obtained from the current literature. Tracers were also used to determine the major reactions producing and destroying hydroxyl radical, because of its role in removing pollutants from irradiated air. Modeling results for selected species have been presented for 1 atmosphere of air at 298.15 K and 50{\%} relative humidity, at doses of 1, 5, 10, 25, and 50 kGy delivered over 0.8 seconds to a static sample. The concentrations of the most abundant ions, radicals, and stable reaction products are reported, and the major reactions producing and destroying hydroxyl radical are quantified. [Preview Abstract] |
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URP.00081: Influence of the pulse-periodic discharge on ignition and laminar flame propagation of methane and ethylene Boris Potapkin, Maxim Deminsky, Marina Strelkova, Irina Chernysheva, Igor Kochetov, Anatolii Napartovich, Seyed Saddoughi, John T. Herbon, Timothy Sommerer Influence of non-equilibrium plasma on ignition and combustion of hydrocarbons are investigated theoretically and experimentally now intensively. In our previous work [1] we have shown that the problem of correct description of influence of non-equilibrium plasma on hydrocarbon combustion can be solved taking into account the effect of active species of plasma on initiation of low-temperature branch of hydrocarbons oxidation. Therefore the development of model where plasma and chemical processes are closely coupled is the key for predictive modeling of such phenomena. The model of pulse-periodic barrier discharge was elaborated and demonstrated reasonable agreement with experiments [2] of ignition of methane and ethylene. Advantages of the non-thermal plasma initiation of combustion over the pure thermal acceleration are discussed. \\[4pt] [1] M. Deminsky et al, ISPC 18, 2009, Bochum, Mechanism of influence of the pulse-periodic discharge on low temperature oxidation of hydrocarbons [2] E. Mintusov et.al, 46th AIAA Aerospace Sciences Meeting, 7 - 10 January 2008, Reno, Nevada, 7, 26, (2009). [Preview Abstract] |
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URP.00082: Electron-Beam Generated Air Plasma Measurement Details: I/Q Detector and Effect of Reduced Electric Field Robert Vidmar, Anusha Uppaluri, Kenneth Stalder An in-phase (I) and quadrature (Q) microwave detector operating at 10 GHz is used to measure the electron number density and momentum-transfer collision rate of air plasma as a function of pressure from 1 mT to 636 T and reduced electric field. Raw measurements from the I/Q detector and the method to convert such measurement into electron number density and momentum transfer collision rate are discussed. Optical emissions at 391.4 nm from N$_{2}^{+}$ are used to quantify the volumetric ionization profile along the microwave propagation path. At low pressure a MAGIC code calculation provides the relative ionization profile. Results of electron number density and momentum-transfer collision rate are shown as a function of reduced electric field and pressure. [Preview Abstract] |
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URP.00083: Mechanism of methane dry reforming using an arc-jet plasma reactor Hwang Na Kyung, Cha Min Suk, Hur Min, Song Young-Hoon The characteristics of plasma reaction for dry reforming of methane have been studied using an arc-jet plasma reactor with AC power supply. The effects of the operating parameters, which are input power, CO$_{2}$/CH$_{4}$ ratio, added O$_{2}$ ratio, and the portion of CH$_{4}$+CO$_{2}$ amount in reactants, were investigated by product analysis. As results, the decompositions of CH$_{4}$ and CO$_{2}$ were enhanced by input electrical power. The amount of produced hydrogen was affected by the supplied power and the portion of CH$_{4}$+CO$_{2}$ in the reactants, demonstrating increasing behavior with increasing supplied power and the volume of CH$_{4}$ and CO$_{2}$. For fuel based energy efficiency, the effect of the supplied power was neutral, while the CO$_{2}$/CH$_{4}$ ratio and the portion of CH$_{4}$ +CO$_{2}$ amount gave a positive impact to the efficiency. Moreover, we could get various H$_{2}$/CO ratio ranged 0.8 -- 2.5 by controlling the CO$_{2}$/CH$_{4}$ ratio. Detailed mechanism and characteristics of the dry reforming of methane will be discussed also. [Preview Abstract] |
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URP.00084: Optical and electrical characterization of atmospheric pressure microplasma for CH$_{3}$OH/H$_{2}$O/Ar mixtures Jin Hoon Cho, Young Dong Park, Myeong Yeol Choi, Woong Moo Lee Atmospheric pressure, non-equilibrium microplasmas have become powerful experimental tools for many applications including microfabrications in microelectronics, surface modifications, environmental processing and many other areas. We investigated that comparative study of atmospheric pressure microdischarge generated in different nonequlibrium discharge with respect to observation optical and electrical characteristics at CH$_{3}$OH/H$_{2}$O/Ar mixtures. This paper focuses on plasma chemical reactions from methanol and water vapor mixture and the effects of plasma generation methods in the perspective of hydrogen generation. The microplasmas were generated by resorting to discharge modes such as some variations of glow dielectric barrier discharge (DBD) and also a variation of corona discharge called a microdischarge inside a porous ceramic (MIPC). Plasma chemical reactions were monitored using optical emission spectroscopy to gather information on the degree of non-equilibrium, electron density, uniformity of plasma reaction and concentrations of transient species. [Preview Abstract] |
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URP.00085: Analysis of Optical Spectra Measured in Plasma-Based Tissue Removal System Myeong Choi, Il Gyo Koo, Cameron Moore, George Collins An atmospheric pressure plasma used for tissue removal is characterized based on emission spectroscopy. This type of plasma system, which produces large concentrations of reactive chemical species, demonstrates potential application to tissue processing. The plasma is generated using radio frequency (RF) power that is delivered through the dielectric barrier of a quartz tube. In particular we identify gas phase species and estimate their relative concentrations with varying amounts of delivered power, chemical flow, and amount of tissue removal. [Preview Abstract] |
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URP.00086: PLASMA BOUNDARIES: SHEATHS, BOUNDARY LAYERS, OTHERS |
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URP.00087: A simulation of a capacitively coupled oxygen discharge using the oopd1 particle-in-cell Monte Carlo code J.T. Gudmundsson, M.A. Lieberman, Ying Wang, J.P. Verboncoeur The oopd1 particle-in-cell Monte Carlo (PIC-MC) code is used to simulate a capacitively coupled discharge in oxygen. oopd1 is a one-dimensional object-oriented PIC-MC code [1] in which the model system has one spatial dimension and three velocity components. It contains models for planar, cylindrical, and spherical geometries and replaces the XPDx1 series [2], which is not object-oriented. The revised oxygen model includes, in addition to electrons, the oxygen molecule in ground state, the oxygen atom in ground state, the negative ion O$^-$, and the positive ions O$^+$ and O$_2^+$. The cross sections for the collisions among the oxygen species have been significantly revised from earlier work using the xpdp1 code [3]. Here we explore the electron energy distribution function (EEDF), the ion energy distribution function (IEDF) and the density profiles for various pressures and driving frequencies. In particular we investigate the influence of the O$^+$ ion on the IEDF, we explore the influence of multiple driving frequencies, and we do comparisons to the previous xpdx1 codes. [1] J. P. Verboncoeur, A. B. Langdon, and N. T. Gladd, Comp. Phys. Comm. 87 (1995) 199 [2] J. P. Verboncoeur, M. V. Alves, V. Vahedi, and C. K. Birdsall, J. Comp. Physics 104 (1993) 321 [2] V. Vahedi and M. Surendra, Comp. Phys. Comm. 87 (1995) 179 [Preview Abstract] |
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URP.00088: Studies and comparison of currently utilized models for ablation in Electrothermal-chemical guns Shenli Jia, Rui Li, Xingwen Li Wall ablation is a key process taking place in the capillary plasma generator in Electrothermal-Chemical (ETC) guns, whose characteristic directly decides the generator's performance. In the present article, this ablation process is theoretically studied. Currently widely used mathematical models designed to describe such process are analyzed and compared, including a recently developed kinetic model which takes into account the unsteady state in plasma-wall transition region by dividing it into two sub-layers, a Knudsen layer and a collision dominated non-equilibrium Hydrodynamic layer, a model based on Langmuir Law, as well as a simplified model widely used in arc-wall interaction process in circuit breakers, which assumes a proportional factor and an ablation enthalpy obtained empirically. Bulk plasma state and parameters are assumed to be consistent while analyzing and comparing each model, in order to take into consideration only the difference caused by model itself. Finally ablation rate is calculated in each method respectively and differences are discussed. [Preview Abstract] |
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URP.00089: Comparison of sheath thickness obtained from the theories of ion correction in the floating potential Hyeong Sik Han, Kwang Tae Hwang, Ik Jin Choe, Chin Wook Chung In the cold plasmas, when the cylindrical probe is used to measure the ion density, an expansion of the sheath thickness related to the sheath voltage increases the ion current. The expansion of the sheath thickness results in an incorrect measurement of ion current. To measure ion density correctly, the sheath thickness should be considered. In the collisionless sheath, the sheath thickness can be calculated by the Child- Langmuir (CL) theory or the Allen-Boyd-Reynolds(ABR) theory. We measured the sheath thicknesses using the floating harmonics method [1] and the cut-off method by the microwave [2], and the results compared with the CL theory [3] and ABR theory [4] in the floating potential. The sheath thicknesses obtained from the ABR theory were in good agreement with the experimental results. \\[4pt] [1] M. H. Lee, S. H. Jang and C. W. Chung, J. Appl. Phys., 101, 033305 (2007)\\[0pt] [2] J.H. Kim, S.C. Choi, Y.H. Shin, and K. H. Chung, Rev. Sci. Instrum. 75, 2706 (2004)\\[0pt] [3] FF Chen, JD Evans, D Arnush, Phys. Plasmas 9, 1449 (2002)\\[0pt] [4] F. F. Chen and D. Arnush, Phys. Plasmas 8, 5051 (2001) [Preview Abstract] |
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URP.00090: Experimental observation of multiple reflections of highly energetic electron beams by the boundary sheaths in capacitive discharges Edmund Sch\"ungel, Julian Schulze, Uwe Czarnetzki In capacitively coupled radio frequency (CCRF) discharges operated at low pressures stochastic electron heating is dominant. It leads to the acceleration of highly energetic electron beams by the expanding plasma boundary sheaths. Such beams can propagate through the entire plasma bulk at low enough pressure and low enough electron-neutral collision frequencies. In 1991 Wood et al. [1] demonstrated by a PIC simulation that under certain conditions such electron beams can be reflected several times between the opposing boundary sheaths. This effect leads to an enhanced confinement of highly energetic electrons in the discharge. Here these reflections are observed experimentally in CCRF discharges of different geometries including the case that the plasma is in contact with a floating wall and that it is confined between two electrodes (powered and grounded) of equal surface areas by a glass cylinder. Phase resolved optical emission spectroscopy is verifying the previously obtained simulation results. \\[4pt] [1] Wood B. P. PhD thesis, University of California at Berkeley, 1991 [Preview Abstract] |
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URP.00091: Are there double layers in unmagnetized electronegative plasmas? Chi-Shung Yip, Noah Hershkowitz Bounded electronegative plasmas are predicted to have electropositive halos. A recent experiment [1] showed that for a negative ion to electron concentration ratio of $\alpha $=0.43 for an Argon-Oxygen plasma a positive halo was a consequence of negative ion satisfying a Boltzmann relation. When Te/T- is greater than 5+$\surd $24 [2] and that $\alpha $ is greater than Te/T- [3], the negative ions are predicted to be confined by a double layer. Experiments are reported in Ar-SF6 and Ar-Cl2 plasmas aimed at finding the double layer by varying the gas concentrations. Experiments are carried out in a filament discharge in a multi-dipole chamber, with no magnetic field on the end walls. An unmagnetized boundary of the plasma is set by a bias plate along the axial direction of the chamber. Negative ion concentrations are determined from the phrase velocity of C.W. Ion Acoustic Waves. Electron temperature and density are determined using Langmuir probes. Plasma potentials are determined by emissive probes. Argon drift velocities are determined by Laser Induced Florescence. [1] Ghim, YC and Hershkowitz, N, Applied Physics Letters. \textbf{94}, 15, 151503 (2009) [2] N. Braithwaite and J. E. Allen, J. Phys. D: Appl. Phys. \textbf{21}, 1733 (1988) [3] R. N. Franklin, Plasma Sources Sci. Technol. \textbf{11}, A31, (2002) [Preview Abstract] |
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URP.00092: PLASMA TOPICS |
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URP.00093: Plasma Assisted Combustion in a Supersonic Flow Hyungrok Do, Seong-kyun Im, Mark Cappelli, Mark Mungal ~A nanosecond pulsed plasma discharge is used to ignite jet (hydrocarbon and hydrogen) flames in supersonic air cross flows (Ma = 1.7 to 3.0). The flow pattern and shockwaves induced by the fuel jets and flow disturbances are characterized by Schlieren imaging. Planar laser induced fluorescence and emission spectroscopy are employed for imaging the distribution of OH radicals. Two common test model flow configurations (cavity and flat wall) are used with integration electrodes for plasma excitation. Cavity flames are found to be readily enhanced by plasma excitation, with a clear reduction in ignition delay time. However, flame propagation beyond the cavity is limited. A flat wall configuration combining an upstream subsonic oblique fuel jet and a downstream sonic transverse fuel jet is shown to provide a more favorable flow condition for jet flame ignition and propagation. The OH distribution in the vicinity of the discharge confirms jet flame ignition by the plasma. Experimental results are validated using a simple theoretical/numerical model. The reduction in the ignition delay and other qualitative features are validated by the model. [Preview Abstract] |
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URP.00094: Arc plasma assisted purification of metallic silicon for solar cells: numerical modeling and real time process monitoring Junghoon Joo, Wonkyun Yang, Bo-Yun Jang, Young Soo Ahn For achieving the grid parity in solar cell business, cheaper materials and processing technology are necessary. Thin film solar cell could be a strong candidate. Ribbon type polycrystalline solar cell may be a low cost solution with much simpler equipments: melting and specialized casting devices. For further reduction of the manufacturing cost, device grade of silicon starting material (99.99999\%) should be replaced with cheaper substitute without degrading the solar conversion efficiency. To reduce the complicated chloride based purification steps, simple vacuum arc melting and purification are considered. It is using small amount of reactive gases (hydrogen or water vapor) under certain plasma conditions to remove B and P through formation of highly volatile oxides and hydrides. Due to the low electrical conductivity of metallic grade silicon, non-transferrable arc operation mode was selected. We used 3D CFD based numerical modeling to optimize the process conditions; arc to silicon pool distance, plasma power input and reactive gas mixing ratio. As a real time monitoring technique, QMS and OES were used to detect any volatile species related with impurities during melting and purification steps. [Preview Abstract] |
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URP.00095: INNOVATIVE PLASMA APPLICATIONS |
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URP.00096: Application of pulsed plasma thruster to materials processing Takashi Kimura, Masayasu Iida, Akinori Oda 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. Electrical and optical measurements of PPA are carried out. From the measured waveforms of the voltage applied between the electrodes and the current, the maximum of the instantaneous power is on the order of MW and the maximum of current is on the order of kA during a short time of 5-10$\mu$s. On the other hand, the optical emission intensities emitted from the excited carbon and fluorine atoms are predominant. This fact should indicate the possibilities of diamond-like-carbon coating or Si etching without a parent gas such as hydrocarbon gas and fluorocarbon gas. [Preview Abstract] |
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URP.00097: Industrial Applications to the Inertial Electrostatic Confinement Configuration Elijah Martin, Steve Shannon, Mohamed Bourham Since Fransworth's observation of inertial electrostatic confinement in the 1930's several applications have been proposed and studied with fusion being the main focus. Inertial electrostatic confinement is a scheme in which ions are focused and confined by means of either an electrostatic field or a combination of electrostatic and magnetic fields to produce an effective spherical potential well. Due to the spherical symmetric configuration and the convergent non-Maxwellian ion beams IEC presents a unique energy spectrum that could enhance or enable a variety of industrial plasma applications from material processing to light sources. This work will present the possible industrial applications of the IEC configuration and initial characterization of an IEC source for these applications. The current industrial applications under consideration include materials synthesis, processing, and light production. [Preview Abstract] |
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URP.00098: AC Excited Si Microplasma Channel Devices: Photon amplification through microchannels Taek Lim Kim, Eung Soo Kim, Efrain Mejia, Sung-Jin Park, James Gary Eden In this presentation, we report the design and performance of ac-excited Si micro-plasma ``V-grooved'' channel devices. These Si channels have been fabricated by anisotropic etching and the width of the channels ranges from 50 to 100 microns and the length ranges from 2 to 5 cm. The V-grooved microchannel generates and confines stable microdischarge in Ne or Ar gas pressures above 400 Torr with the ac excitation of 20 kHz. Radiative intensity from the microplasma is dependent on the channel length, gas pressure and direction. The ratio of photon flux at the transverse and the vertical direction is about 10:1. Furthermore, strong infrared wavelength transitions from Ne or Ar/Xe gas mixtures were also observed at the transverse direction through the microchannel. The optical amplification and radiative efficiency through these devices are characterized with the function of microchannel geometry and dimension. [Preview Abstract] |
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URP.00099: COMPUTATIONAL METHODS FOR PLASMAS |
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URP.00100: Simulation of Chemical Reactions of an Atmospheric Pressure DBD using Graphics Processing Unit Philipp Mertmann, Priyadarshini Rajasekaran, Nikita Bibinov, Peter Awakowicz, Thomas Mussenbrock, Markus Gebhardt A dielectric barrier discharge in air for biomedical applications is characterized by numerical simulations. Plasma in air produces species like $\mathrm{NO}$ or $\mathrm{O}_3$, which are of special interest for medical application due to their potential of reacting on surfaces. Optimisation of plasma conditions to produce required density of these species is simulated using different experimental parameters. Input values for the simulation are obtained by optical emission spectroscopy, current-voltage measurements and micro- photography. Solving diffusion equation considering the gain and loss of particles by plasma-chemical reactions in a transient differential equation can be parallelized very efficiently. The use of a graphics processing unit (GPU, graphics card) for calculations allows for quick solutions of this problem. Performance tests showed that the run-time could be decreased by a factor of about $240$, compared to a conventional CPU and thereby from a couple of days to $25$ minutes. [Preview Abstract] |
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URP.00101: Feature Profile Simulator Algorithm Utilizing Finite Penetration Depth Paul Moroz Fast particles, such as ions or fast neutrals, coming to the material surfaces in plasma etch systems typically possess enough energy to penetrate many mono-layers into materials, leading to the volume-type reactions. This is very different from typical low-energy gaseous species that could interact only with the upper mono-layer. Our feature profile algorithm represents materials as consisting of cells. The cell size could vary from the smallest (containing a single atom) to a very large one containing many mono-layers of atoms. The penetration depth and energy loss in mono-layers is calculated for each fast incoming particle and is used in calculation of its fate and the following reaction mechanisms. Results obtained with the corresponding feature profile simulator FPS, currently, for 2D3V cases (two-dimensional in space with three velocity components of incoming particles) will be presented. [Preview Abstract] |
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URP.00102: Modelling of Low Pressure Breakdown by a Monte Carlo Technique Marija Savic, Marija Radmilovic-Radjenovic, Zoran Petrovic It was recently shown that the basic assumption of Townsend's theory that ions produce the secondary electrons is correct only in a very narrow range of conditions [1]. According to the revised Townsend's theory [1] secondary electrons required to maintain the discharge are produced in collisions of ions, fast atoms, metastable atoms and photons with the cathode or by gas phase ionization mainly by fast neutrals. In this paper, we have tried to build up a procedure for obtaining the secondary electron yields from the gas breakdown data motivated by the fact that published results for the secondary electron yields from ion beam experiments and gas discharges are systematically in serious disagreement. For that purpose, we use a Monte Carlo code that is not limited by assumptions of the energy distribution function and that includes gas phase and surface collisions in arbitrary number and degree of complexity of representation. The results provide partial contributions of different processes and are in general, if not in all detail in agreement with [1]. Argon as a test was the first obvious target of study with calculations being extended to other gases. \\[4pt] [1] A.V. Phelps and Z.Lj. Petrovi\'{c}, {\it Plasma Sources Sci. Technol.} \textbf{8} (1999). [Preview Abstract] |
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URP.00103: 3D simulations of surface roughness in nanotechnologies Marija Radmilovic-Radjenovic, Branislav Radjenovic Plasma etching represents one of the basic steps used in semiconductor processing for the fabrication of electronic devices. One of the limiting factors in applications of plasma etching in new generations of plasma technologies is controlling of plasma induced roughness or surface roughness by plasma etching. Decreasing the roughness of a surface will usually increase exponentially its manufacturing costs. This often results in a trade-off between the manufacturing cost of a component and its performance in application. In this paper we have studied roughening of nanocomposite materials during plasma etching for by using a level set method [1]. It was found that the presence of two phases with different etch rates affects the evolution of the surface roughness. The obtained results apart from their theoretical relevance, have practical implications for surface treatment of nanocomposite materials. \\[4pt] [1] M. Radmilovi\'{c}-Radjenovi\'{c}, B. Radjenovi\'{c} and Z.Lj. Petrovi\'{c}, {\it Thin Solid Films} \textbf{517} (2009) 3954. [Preview Abstract] |
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URP.00104: Three dimensional simulations of the anisotropic wet etching of silicon Marija Radmilovic-Radjenovic, Branislav Radjenovic In this paper we have shown that profile evolution during anisotropic wet etching of silicon can be described by the non- convex Hamiltonian arising from the Hamilton-Jacobi equation for the level set function. Angular dependence of the etching rate is calculated on the base of the silicon symmetry properties, by means of the interpolation technique using experimentally obtained values of the principal [100], [110], [111] directions in KOH solutions. Some examples illustrating developed methodology are presented. The obtained simulaction results inidcate that inclusion of additional directions for which the etching rates are known, would lead to the better quantitative agreement with the measured data. [Preview Abstract] |
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URP.00105: Modeling of self organization in Xe micro hollow cathode discharges Haruaki Akashi Recently, self organization discharges in Xe micro hollow cathode discharges(MHCDs) have been obtained. The discharge is sustainable in DC, not like dielectric barrier discharge(DBD). Stollenwerk et al[1] reported the self organized pattern in DBD is related to the accumulated charge on the dielectric. In DBD, self organized patterns are significantly affected by dielectric, however, it is not known yet in MHCD. To clarify the mechanism, the simulation has been started. Cylindrical symmetric two dimensional fluid model is taken. The fluid model is adapted from the ref.[2]. The electrodes configuration is similar to ref.[3]. Negative voltage is applied to cathode. In this condition, the self organization pattern is not shown, but the discharge becomes glow like discharge as written in ref.[3]. The peak of electron density is obtained slightly above the hole, but the excimer and ions density peaks are obtained in the hole.\\[4pt] [1] L.Stollenwerk et al. Phys.Rev.Lett.,96,255001(2006)\\[0pt] [2] H.Akashi et al, IEEE Trans.Plasma Sci.,33,2,308(2005)\\[0pt] [3] W.Zhu et al, J.Phys.D: Appl.Phys.,40,3896(2007) [Preview Abstract] |
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URP.00106: Particle-In-Cell simulations of high pressure plasmas using graphics processing units Markus Gebhardt, Frank Atteln, Ralf Peter Brinkmann, Thomas Mussenbrock, Philipp Mertmann, Peter Awakowicz Particle-In-Cell (PIC) simulations are widely used to understand the fundamental phenomena in low-temperature plasmas. Particularly plasmas at very low gas pressures are studied using PIC methods. The inherent drawback of these methods is that they are very time consuming -- certain stability conditions has to be satisfied. This holds even more for the PIC simulation of high pressure plasmas due to the very high collision rates. The simulations take up to very much time to run on standard computers and require the help of computer clusters or super computers. Recent advances in the field of graphics processing units (GPUs) provides every personal computer with a highly parallel multi processor architecture for very little money. This architecture is freely programmable and can be used to implement a wide class of problems. In this paper we present the concepts of a fully parallel PIC simulation of high pressure plasmas using the benefits of GPU programming. [Preview Abstract] |
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URP.00107: Numerical Simulation of Cold Dense Plasma Sputtering with VORPAL Chuandong Zhou, Peter Stoltz, Seth Veitzer Sputtering is an evaporation process that physically removes atoms from a solid target material. This process takes place under bombardment of the target surface by energetic ions. Sputtering is widely applied in material processing and coating, such as etching and thin film deposition. Numerical simulation of sputtering process requires both accurate models of nuclear stopping in materials, particle dynamics and consistent electromagnetic fields. The particle in cell code VORPAL can simulate cold dense plasma under many different electromagnetic configurations. The dynamics of both incident particles and sputtered neutral atoms are simulated in VORPAL, and the sputtering yield is calculated from a standalone numerical library for a variety of materials that are commonly used in industrial applications. Numerical simulation of the spatial distribution of sputtering resulting from a cold dense plasma under externally applied magnetic field and self-consistent electric field is presented. [Preview Abstract] |
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URP.00108: Benefits of Higher-Order Particles in Simulating an Overdense Plasma Using a Particle-in-Cell Code Christine M. Roark, Paul Mullowney, Kevin Paul, David Smithe, Peter H. Stoltz Researchers often would like to apply Particle-in-Cell (PIC) methods to model cold, high pressure plasmas in order to discern any kinetic, nonlinear or space charge effects. However, the PIC method typically does not preform well at low temperatures and high densities due to limitations on time and space scales for numerical and practical reasons. One of these limitations is the requirement to resolve the Debye length. Failure to resolve the Debye length in a PIC simulation typically results in artificial heating of the plasma known as grid heating. For applications such as plasma processing, the rate of plasma production is a sensitive function of the electron temperature, so grid heating can make simulation results entirely unreliable. The use of higher-order particle algorithms that smooth out the particle current and charge can help to eliminate this unphysical heating and allow cold, dense plasmas to be simulated using PIC. We present results of using higher-order particles for modeling an overdense plasma sustained by microwaves and we compare to results using standard first-order particles. Specifically, we compare the electron temperature, sheath size, and rate of plasma formation for simulations with an argon gas of 0.05 Torr pressure with an applied microwave power of 1000 Watts at 2.45 GHz. [Preview Abstract] |
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