Bulletin of the American Physical Society
68th Annual Gaseous Electronics Conference/9th International Conference on Reactive Plasmas/33rd Symposium on Plasma Processing
Volume 60, Number 9
Monday–Friday, October 12–16, 2015; Honolulu, Hawaii
Session LW1: Poster Session II (4:00pm - 6:00pm) |
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Room: Exhibit Hall III |
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LW1.00001: CHARGED PARTICLE COLLISIONS II |
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LW1.00002: Low energy elastic scattering from toluene Ahmad Sakaamini, Leigh Hargreaves, Murtadha A. Khakoo, Diego Farago Pastega, Marcio H.F. Bettega Differential scattering cross sections for elastic scattering of low-energy electrons from toluene are presented in the form of experimental and theoretical (Schwinger multichannel method with pseudopotentials) results. The experimental incident electron energy range is from 1eV to 20eV and scattering angles from 15 to 130 degrees. Comparisons with other available cross sections are also presented. [Preview Abstract] |
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LW1.00003: Excitation of atmospheric species by electron impact Paul V. Johnson, Xianming Liu, Charles P. Malone, Jeffrey D. Hein, Murtadha A. Khakoo Electron collisions with atmospherically relevant neutral molecular targets, such as H$_{2}$ and N$_{2}$, have been investigated. Resulting fluorescence was probed using various monochromator-detector combinations, such that photon intensities were investigated as a function of wavelength and incident electron energy. In addition, electron energy-loss spectroscopy (EELS) was utilized such that differential cross sections (DCSs) and integral cross sections (ICSs) were obtained. The measured emission cross sections, DCSs, and ICSs, as well as calculations of spectroscopic parameters, for these atmospheric species will be presented. [Preview Abstract] |
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LW1.00004: Low-energy electron impact excitation of ethanol Leigh Hargreaves, Kenneth Varella, Murtadha Khakoo, Carl Winstead, Vince McKoy We present differential cross sections measurements for excitation of the four lowest-lying states of ethanol by low energy electrons. The measurements were obtained using an electron energy loss spectrometer with a moveable aperture gas source, and employing a least squares fitting routine to unfold the overlapping contributions of each transition in the measured spectra. Data was taken at scattering angles ranging from 15 -- 130 degrees, and incident energies between 9 and 20 eV. The measurements are compared with current theoretical calculations, and previous results for excitation of methanol and water. [Preview Abstract] |
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LW1.00005: Polarized electron correlations near auto-ionizing states of zinc atoms James Williams, Luka Pravica, Sergey Samarin Multi-electron metal atoms find new applications in diverse structures with spin and momentum-dependent properties having significance in determining material functionalities. Electron correlations effects are determined from scattering kinematics of spin-polarized electrons exciting zinc atoms near autoionizing states up to 16 eV. Previous studies of the 4$p^{3,1}P_{1}$, 4$d$,5$d$,6$d^{3}D_{1,2,3}$ and 4$d$,5$d^{1}D_{1}$ excited states observed photon decay intensities and scattered electron energies and angles in the energy region of the 3$d^{9}$4$s^{2}$4$p $autoionizing states up to 12 eV [1]. Strong electron correlations and active roles of 3$d $electrons were evident. Our observations of the 5$^{3}$S excited state for electron energies up to 16 eV show dominant 3$d $core-excited negative-ion resonances and strong Post-Collision Interaction (PCI). For low energies of scattered and ejected electrons, after near-threshold excitation of the 3$d^{9}$4$s^{2}$4$p $autoionizing states, a large transfer of orbital angular momentum is evident. Results include angular differential elastic scattering and excitation functions, ``integrated'' Stokes polarization parameters and spin up/down asymmetries indicating spin-orbit interaction and electron exchange effects.\\[4pt] [1] S. Napier et al Phys Rev A 78 (2008) 032706 [Preview Abstract] |
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LW1.00006: Electron ionization and ion-molecule reactions of triethylborane Charles Jiao, Steven Adams Triethylborane (TEB) is used as a radical initiator in many chemical reactions and as an excellent ignition source for jet engines and rocket engines. In this paper we will report our recent study on the ion chemistries of TEB relevant to the charged particle processes in plasmas involving TEB. The total cross section of electron ionization of TEB is found to have a maximum of 2.2x10$^{-15}$ cm$^{2}$ at 75$+$10 eV electron energy. Product ions from the ionization include C$_{2}$H$_{2-5}^{+}$, BCH$_{4}^{+}$, BC$_{2,4,6}^{+}$, BC$_{3}$H$_{4,6}^{+}$, BC$_{4}$H$_{8,10}^{+}$ and BC$_{6}$H$_{15}^{+}$, among which BC$_{6}$H$_{15}^{+}$, BC$_{4}$H$_{10}^{+}$ and BC$_{2}$H$_{6}^{+}$ are the most abundant ions. These ions react with TEB via various mechanisms including charge-transfer, alkyde-transfer and association reaction. The common and major product ions from the ion-molecule reactions are BC$_{4}$H$_{10}^{+}$ and BC$_{2}$H$_{6}^{+}$, formed by simple ethide-transfer and ethide-transfer followed by dissociation (loss of C$_{2}$H$_{4})$, respectively. [Preview Abstract] |
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LW1.00007: Quasi Sturmian basis in two-electron continuum Coulomb problems Lorenzo Ugo Ancarani, A.S. Zaytsev, M.S. Aleshin, S.A. Zaytsev A new type of basis functions is proposed to describe a two-electron continuum which arises as a final state in electron-impact ionization and double photoionization of atomic systems. These two-particle basis functions are obtained, by analogy with the Green's function of two non-interacting hydrogenic atomic systems, as a (complex energy plane) convolution integral of two one-particle Quasi Sturmian functions [1]. We name these functions Convoluted Quasi Sturmian functions (CQS).~ By construction, a CQS function (unlike a simple product of two one-particle ones) behaves like a six-dimensional outgoing spherical wave when the hyperradius goes to infinity$.$This important property should be useful when solving three-body Coulomb scattering problems. It is the purpose of this contribution to explore the effectiveness of such CQS as a basis set.\\[4pt] [1]~ J. A. Del Punta, M. J. Ambrosio, G. Gasaneo, S. A. Zaytsev and L. U. Ancarani 2014 J. Math. Phys. 55, 052101. [Preview Abstract] |
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LW1.00008: Triple Differential Cross Sections for single ionization of the Ethane molecule Esam Ali, Kate Nixon, Chuangang Ning, Andrew Murray, Don Madison We report experimental and theoretical results for electron-impact (e,2e) ionization of the Ethane molecule (C2H6) in the coplanar scattering geometry for four different ejected electron energies E$_a$=5,10,15, and 20 eV respectively, and for each ejected electron energy, the projectile scattering angle is fixed at $10^{\circ}$. We will show that the TDCS is very sensitive for the case of two heavy nuclei surrounded by lighter H nuclei. On the theoretical side, we have used the M3DW coupled with the Orientation Averaged Molecular Orbital (OAMO) approximation and proper average (PA) over all orientations. These approximations show good agreement with experimental data for the binary peaks. However, for the recoil peak region, experiment finds a noticeable peak while theory predicts no peak. No recoil peak suggests no (or very weak) nuclear scattering, so we have investigated the importance of nuclear scattering by moving the nuclei closer to the center of mass. [Preview Abstract] |
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LW1.00009: Emission and Ionization Cross Sections for Atomic Oxygen Swaraj Tayal, Oleg Zatsarinny The B-spline R-matrix with pseudostates approach has been used to calculate electron collision emission and ionization cross sections for atomic oxygen in the electron energy region up to 150 eV. We included nineteen spectroscopic and 1097 pseudostates in the close-coupling expansion. These states were generated by a combination of B-spline box based multichannel close-coupling expansions and multiconfiguration Hartree-Fock method. The pseudostates cover the energy region up to 50 eV above the ionization limit. The inclusion of pseudostates leads to a better agreement with experimental emission cross sections. Our calculated ionization cross sections are also in very good agreement with available experimental data. The comparison of different scattering models and experiments provides an estimate of accuracy of our results. [Preview Abstract] |
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LW1.00010: Computational Study on Chemical Reaction Mechanisms of Octafluorocarbon Molecules Heechol Choi, Mi-Young Song, Jung-Sik Yoon Saturated or unsaturated octafluorocarbons(OFCs) have been used extensively in dry etching processes due to their relatively low global warming potential and their high CF$_{2}$ radical levels in commercial plasma treatments. Many experimental and theoretical studies of these species have been performed for useful information about physical and chemical properties of OFCs. However, direct experimental studies of these chemicals are difficult because of their high reactivity in plasma state and high-level theoretical approaches such as G3(MP2) and CCSD(T)/CBS need huge computational cost. Recently, it has been shown that the $\omega $B97X-D/aVTZ method is strongly recommended as the best practical density functional theory(DFT) for rigorous and extensive studies of OFCs because of its high performance and reliability for van der Waals interactions. All the feasible isomerization and dissociation paths of OFCs were investigated at $\omega $B97X-D/aVTZ and rate constants of their chemical reactions were computed by using variational transition-state theory(VTST) for a deep insight into OFCs' reaction mechanisms. Fates and roles of OFCs and their fragments in plasma phases could be clearly explained based on the obtained reaction mechanisms. [Preview Abstract] |
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LW1.00011: Gas Phase Dissociative Electron Attachment to Formamide Derivatives NMF and DMF Zhou Li, M. Michele Dawley, Sylwia Ptasinska Fragmentation of biomolecules, such as nucleobases, induced by low energy electrons can lead to the break of DNA strands. Dissociative electron attachment (DEA), which can occur due to low energy interactions, is initiated with the formation of transient negative ions which exhibit characteristic resonant profiles in the product ion yield. The consequent fragmentation process can either be as simple as a single bond cleavage or a relatively complex process involving multiple bond rearrangements. Measurements of resonant peaks in ion yields and identification of ion products provide information of the resonant energies of the parent molecules as well as the fragmentation pathways. N-methylformamide (NMF) and dimethylformamide (DMF) are both derivatives of formamide which is the simplest structure containing the peptide bond linkage. In this work we identified anion fragments and measured resonance profiles of produced anions due to DEA to NMF and DMF. The anionic species produced from the two molecules were compared as well as the resonant positions and ion yields. Based on this comparison, the DEA process to the two molecules bears similarities such as leading to breaking of peptide bonds (C-N), as well as discrepancies such as absence of OCN$^{-}$ in DEA to DMF. The selective property of H atom loss, which is reported in the DEA to formamide, is also justified in our experiment since no dehydrogenated DMF anion was detected. [Preview Abstract] |
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LW1.00012: Plasma Decay in Oxygen-Containing Mixtures Excited by High-Voltage Nanosecond Discharge Eugeny Anokhin, Maksim Popov, Igor Kochetov, Andrey Starikovskiy, Nikolay Aleksandrov Atoms and radicals produced in the discharge plasma possess excessive translational energy (a few electron-volts) The results of experimental and numerical study of the high-voltage nanosecond discharge afterglow in CO$_{\mathrm{2}}$:O$_{\mathrm{2}}$ and Ar:O$_{\mathrm{2\thinspace }}$mixtures are presented for room gas temperature and a pressure of 10 Torr. Electron density during the plasma decay was measured with a microwave interferometer for initial electron densities in the range between 10$^{\mathrm{12}}$ and 10$^{\mathrm{13}}$ cm$^{\mathrm{-3}}$. Plasma properties in the discharge afterglow were numerically simulated by solving the balance equations for charged particles and electron temperature. Calculations showed that the dominant positive ion species was O$_{\mathrm{2}}^{\mathrm{+}}$ and that the loss of electrons was controlled by dissociative and three-body recombination with these ions. An agreement between the measured and calculated values of electron density during plasma decay in air and pure oxygen was reached only under the assumption that the rate of three-body electron recombination with O$_{\mathrm{2}}^{\mathrm{+}}$ ions is much higher than the rate of thoroughly studied three-body recombination for atomic ions. Based on the analysis of the experimental data, the rate of three-body recombination with O$_{\mathrm{2}}^{\mathrm{+}}$ ions was extracted for thermal electrons and for electron temperatures up to 6000 K. [Preview Abstract] |
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LW1.00013: Modeling molecules responsible for the sidewall protection during the chemical dry etching of silicon related materials using F$_{2} + $ NO$_{x} \to $ F $+$ FNO$_{x}$ Satomi Tajima, Toshio Hayashi, Koji Yamakawa, Minoru Sasaki, Kenji Ishikawa, Makoto Sekine, Masaru Hori We have been investigating the chemical dry etching of Si related materials using the reaction of F$_{2} + $ NO$_{x}$ (X $=$ 1, 2) $\to $ F $+$ FNO$_{x}$. In our previous study, we found that this chemical dry etching technique generated anisotropic etching profile when the substrate temperature was maintained at \textless 60$^{\circ}$C. In this study, we evaluated the cause of the anisotropic etching by measuring the molecules present in the gas phase by Fourier Transform Infrared Spectroscopy (FTIR) followed by calculating the chemical bonding structure formed on the Si surface by density functional theory (DFT). First the reaction between SiF$_{4}$ and molecules generated by the reaction between F$_{2}$, NO$_{x}$, and adsorbed H$_{2}$O such as F$_{2}$, NO$_{x}$, FNO$_{x}$, H$_{2}$O, OH, and HF, measured by FTIR, were calculated by DFT to identify key molecules that can present in the gas phase. We found that the chemical reaction between SiF$_{4}$ and multiple FNO may play a key role to prevent the sidewall etching. The modeling at the surface reaction using DFT is in progress. [Preview Abstract] |
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LW1.00014: CAPACITIVELY COUPLED PLASMAS |
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LW1.00015: Electromagnetic resonances of plasma column between two metallic plates Sergey Dvinin, Vitaly Dovzhenko, Oleg Sinkevich It is known that there are two types of electrodynamic resonances of bounded supercritical plasma, placed between the two metal planes are possible. The first type is associated with the excitation of surface waves propagating along the lateral surface [1]. The second one is caused by standing surface waves in the sheath at plasma-metal boundary [2 -- 4]. This work is concerned with theoretical study of the resonance properties of plasma slab in cases where both effects can be observed together. Resonance densities and frequencies are calculated. Solution of Maxwell's equations is demonstrated that directions of energy flows in first and second cases are opposite. Energy transfer to lateral surface waves is prevailing, if the field frequency is higher than the frequency, corresponding to the geometric plasma-sheath resonance [5]. Amplitude of waves at plasma metal boundary becomes greater in opposite case. Discharge properties in both cases are calculated including joint excitation.\\[4pt] [1] S. Dvinin et al., Sov. Phys.: Fizika Plazmy, 9, 1297 (1983).\\[0pt] [2] M.A. Lieberman, J.P. Booth, P. Chabert et al., Plasma Sources Sci. technol., 11, 283 (2002).\\[0pt] [3] S.A. Dvinin, A.G. Vologirov, V.V. Mikheev et al., Plasma Physics Reports, 34, 688 (2008). \\[0pt] [4] W. Gekelman, M. Barnes, S. Vincena et al., Phys. Rev. Lett., 103, 045003 (2009). \\[0pt] [5] J. Taillet. American Journal of Physics, 37, 423 (1969). [Preview Abstract] |
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LW1.00016: Filamentation of capacitive Radio-Frequency discharge at low pressures Sergey Dvinin, Zafari Kodirzoda It is known that ionization instability may occur in high-frequency (HF) discharges, resulting in breaking of uniform plasma density distribution [1 -- 3]. The model [1] dealt with an instability associated with the peculiarities of transfer processes and electron kinetics for non-Maxwellian electron energy distribution function. We consider the stability of capacitive discharge between two cylindrical electrodes with radii R and r at low pressures. It is shown that for large electrodes R--r \textless \textless r the uniform density distribution in the discharge can be unstable. Instability occurs if the frequency of supporting field is higher than geometric plasma-sheath resonance [4] frequency, and the output impedance of the RF generator is large enough. Instability is connected with falling current-voltage characteristics and leads to discharge filamentation. Analytical model, based on equations for filament boundary motion, is developed. The model allows to determine the size of discharge chamber area occupied by plasma, the density of electrons, and current-voltage characteristics. Numerical calculations confirm analytical results.\\[4pt] [1] D. Mackey, L. Planti\'e, M.M. Turner, Appl. Math. Lett., 18, 865 (2005).\\[0pt] [2] J. Schulze, D. Llscher, and U. Czarnetzki, IEEE Transaction on plasma science, 36, 1402 (2008).\\[0pt] [3] S. Dvinin et al., Sov. Phys.: Fizika Plazmy, 9, 1297 (1983).\\[0pt] [4] J. Taillet. American Journal of Physics, 37, 423 (1969). [Preview Abstract] |
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LW1.00017: Electron heating via the self excited plasma series resonance in multi-frequency capacitive plasmas Steven Brandt, Edmund Schuengel, Zoltan Donko, Ihor Korolov, Aranka Derzsi, Julian Schulze In a combined approach of PIC/MCC simulations and a theoretical model based on an equivalent circuit, the self-excitation of Plasma Series Resonance (PSR) oscillations and their effect on the electron heating in geometrically symmetric capacitively coupled radio frequency (CCRF) plasmas driven by multiple consecutive harmonics of 13.56 MHz is investigated. The discharge symmetry is controlled via the Electrical Asymmetry Effect, i.e. by varying the total number of harmonics and tuning the phase shifts between them. It is demonstrated that PSR oscillations of the electron current density will be self-excited, if (i) the charge-voltage relation of the plasma sheaths deviates from a simple quadratic behavior and if (ii) the inductance of the plasma bulk exhibits a temporal modulation. Both effects are neglected in existing models of the PSR, but found to be crucial here. The effect of the PSR self-excitation on other plasma parameters, such as the potential profile, is illustrated by applying Fourier analysis. High frequency oscillations in the entire spectrum between the applied frequencies and the local electron plasma frequency are observed. The electron heating is demonstrated to be strongly enhanced by the PSR and complex electron heating dynamics are observed. [Preview Abstract] |
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LW1.00018: Resonance Phenomena of Voltage and Current Driven Capacitively Coupled Plasmas Sebastian Wilczek, Jan Trieschmann, Julian Schulze, Edmund Schuengel, Ralf Peter Brinkmann, Aranka Derzsi, Ihor Korolov, Zolt\'an Donk\'o, Thomas Mussenbrock The plasma series resonance is a fundamental phenomenon due to the nonlinear interaction between the plasma bulk and the sheaths of a capacitive discharge. It has been proven to play an important role in the context of electron heating. Furthermore, recent results indicate that the manifestation of harmonics in the plasma current due to the plasma series resonance is responsible for a nonlinear standing wave effect and, consequently, spatial inhomogeneities in the power deposition. It is important to note that the plasma series resonance is a current governed resonance and that it can only be excited in voltage driven systems. Particle-In-Cell simulations however show that also in current driven systems resonances can occur due to the non-linear excitation of harmonics in the conduction and displacement current. In this work, the differences between voltage and current driven capacitive discharges in terms of their nonlinear behavior are investigated. It is found that under certain conditions nonlinear plasma parallel resonances are excited which are able to support the electron heating. [Preview Abstract] |
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LW1.00019: Atmospheric Pressure RF Discharge for Nanocrystal Synthesis Narula Bilik, Benjamin Greenberg, Uwe Kortshagen Atmospheric pressure plasmas are inexpensive alternatives to low-pressure plasmas. Constructing such plasmas is a challenge due to the instabilities associated with high pressure. Most RF atmospheric pressure plasmas are microplasmas built to preserve the Paschen's law scaling, leading to small volumes and low production quantity. Here we present a large-volume (non-micro scale) atmospheric pressure plasma for nanocrystal synthesis. The plasma is a dielectric barrier discharge with an average gap spacing of 2.4 mm. The discharge appears uniform viewed by the eye. The gap spacing is non-uniform: discharge is first initiated in a region where the gap spacing is minimum to encourage the formation of free electrons and metastables, then the discharge expands to fill the entire volume as the voltage is increased; this way, the discharge remains uniform over large volume. Zinc oxide nanocrystals with a crystallite size of about 12 nm were produced in the reactor. The shape of the nanoparticles sensitively depends on the residence time. Near-circular particles were produced when using a carrier flow rate of 5 slm, while elongated particles were produced when using a carrier flow rate of 10 slm. [Preview Abstract] |
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LW1.00020: Fluid simulation and experimental measurement of radical densities in capacitively coupled CF$_{4}$/Ar plasma Ying-Shuang Liang, Yong-Xin Liu, Yu-Ru Zhang, Wen-Yao Liu, You-Nian Wang Both of the two-dimensional self-consistent fluid model and the experimental diagnostic method are employed to investigate the effects of the external parameters on the plasma parameters, especially on the production and loss of the CF$_{2}$ and F radicals, in the capacitively coupled CF$_{4}$/Ar plasmas driven at 60 MHz. It is observed that the CF$_{3}$ and F are the two main radicals under all the investigated conditions. With the increase of the discharge power, the densities of the CF$_{2}$ and F radicals increase almost linearly. By comparing the calculated and experimental results, it is found that the main production mechanism of the CF$_{2}$ radical is the electron-impact dissociation of CF$_{4}$. However, the electron-impact dissociation of CF$_{3}$ plays an important role in the production of the F radicals, besides the electron-impact dissociation of CF$_{4}$. The general qualitative agreement between the calculated and the experimental results indicates that the present fluid model correctly describes the CF$_{4}$/Ar capacitive discharge. [Preview Abstract] |
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LW1.00021: Spatial Distribution of Plasma Parameters in an Asymmetric Coaxial Discharge Jeremy Peshl, Janardan Upadhyay, Milka Nikolic, Alexander Godunov, Svetozar Popovic, Leposava Vuskovic Plasma processing of superconductive radio-frequency (SRF) cavities provides the unique opportunity of tailoring the inner surfaces for better SRF properties in addition to being a less expensive and more environmentally friendly method of processing the cavities. An asymmetric coaxial capacitively coupled RF discharge is a natural approach to plasma processing of an SRF cavity. Although the experimental setup and process parameters necessary to generate the reversal of the asymmetry and achieve the 3D surface processing have been established [1], information about the plasma properties such as electron temperature, ion energy, and plasma density remain elusive for asymmetric coaxial capacitively coupled plasmas (CCP). For diagnostic purposes, an RF (15.36 MHz) coaxial CCP is made using a 12'' long and 2'' diameter powered inner electrode and a 12'' long 3.85'' inner diameter outer grounded electrode. Plasma parameters are measured using external and internal optical emission spectrometers and a Langmuir probe. Spatial distributions of plasma parameters are collected by changing the radial positions of the measurement devices. Comparative analysis of the data from each diagnostic tool is conducted to ensure consistency of the quantitative results. \\[4pt] [1] J. Upadhyay, J. Appl. Phys. \textbf{117}, 113301 (2015). [Preview Abstract] |
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LW1.00022: Structure of Velocity Distribution of Sheath-Accelerated Secondary Electrons in Asymmetric RF-DC Discharge Alexander V. Khrabrov, Johan Carlsson, Igor D. Kaganovich, Peter L. Ventzek, Lee Chen Low-pressure capacitively-coupled discharges with additional DC bias applied to a separate electrode find important industrial applications. Prime examples are plasma-assisted etching and deposition technologies. An interesting and important property of such discharges, observed in experiments, is an enhanced and non-monotonic high-energy tail of the electron velocity distribution function (EVDF) near the surface of the RF (a.k.a. powered) electrode. Such structures, at energies of several hundred eV, are possibly caused by secondary electrons emitted from the electrodes and interacting with two high-voltage sheaths; a stationary sheath at the DC electrode and an oscillating, self-biased sheath at the powered electrode. We have performed particle simulations where the features in the EVDF of electrons impacting the RF electrode are fully resolved at all energies. An analytic model has been developed to predict existence of peaked and step-like structures in the EVDF. The latter electrons can be grouped by the number of bounces between the sheaths during their lifetime in the discharge. Each of the groups may give rise to an individual peak in the distribution. Initial particle-in-cell simulations of these effects will be reported. [Preview Abstract] |
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LW1.00023: Particle-in-cell simulations of a large capacitively coupled plasma discharge Denis Eremin, Daniel Szeremley, Thomas Mussenbrock, Ralf-Peter Brinkmann A capacitively coupled low-pressure plasma discharge with large electrode radius (25 cm) and a large grounded side chamber radius (25 cm) is simulated with a particle-in-cell code for different driving frequencies. The simulations reveal the importance of plasma dynamics in the side chamber for the whole plasma discharge. In particular, it is observed that at 60 MHz the plasma density profile in the side chamber features an unexpected hump close to the side chamber entrance. At the same time the self-bias at this frequency virtually vanishes despite large geometrical asymmetry of the reactor, which is also not anticipated in a single-frequency driven discharge. The plasma density profile uniformity exhibits a pronounced frequency dependence as well. [Preview Abstract] |
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LW1.00024: Modeling of dual frequency capacitive discharges with pulse-modulated power input Schabnam Naggary, Efe Kemaneci, Ralf Peter Brinkmann, Mohammed Shihab, Zolt\'{a}n Kov\'{a}cs, Mustafa Megahed Pulse-modulated capacitive discharges provide additional degrees of freedom to modify the characteristic features of plasma constituents and control the ion energy distribution function (IEDF). In addition, dual frequency capacitive discharges enable a functional separation of the sheath voltages and the plasma composition, allowing for a more precise control of the ion energy distribution [1]. In this contribution, a dual frequency pulse-modulated capacitive discharge is numerically studied. In the first part of the investigation, a global model is used to provide a quick assessment of the discharge characteristics. The model consists of two parts, a multimode lumped circuit model and a chemical global model. With an iterative coupling of the two models, the plasma parameters are obtained self-consistently. An analytic sheath model then delivers the IEDF [2,3]. Multiple scenarios are parametrically investigated. Furthermore, a spatially resolved analysis is conducted using the multiphysics tool CFD-ACE+. This is compared with the global modeling approach particularly concerning the key factors accuracy and computational cost.\\[4pt] [1] D Wen et al., J. Appl. Phys. 115 (2014)\\[0pt] [2] M Kratzer et al., J. Appl. Phys. 90 (2001)\\[0pt] [3] M Shihab et al., J. Phys. D: Appl. Phys. 45 (2012) [Preview Abstract] |
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LW1.00025: Capacitively coupled dc/rf discharges driven by arbitrary linear circuits John Cary, Ming-Chieh Lin, David Smithe, Sean Zhou We have developed a method for computing the system of an arbitrary linear circuit coupled to a capacitively coupled plasma discharge. The method relies on the known method of separation of the vacuum and plasma generated fields for the discharge. It is time centered and implicit in the circuit quantities, thus guaranteeing second-order accuracy in time. This method has been implemented in the VSim engine (Vorpal). Numerical verification of the order of accuracy will be shown. [Preview Abstract] |
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LW1.00026: Experimental study of a very high frequency (162MHz) capacitively coupled multi-tile electrode plasma source Nishant Sirse, Bert Ellingboe In the recent years, plasma discharges excited at very high frequency (30-500MHz) has attracted much attention due to its ability to perform etching and deposition of large area substrates. VHF discharges yield high plasma density and low electron temperature and enable enhanced plasma dissociation. However, the plasma chemistry and power coupling mechanism in VHF discharges is not fully understood. In this article, we present an experimental study on nitrogen plasma produced by a VHF (162 MHz) multi-tile electrode. Electron density profile and gas temperature (rotational and vibrational) are measured as a function of rf power (100-1500W) and gas pressure (50mTorr-1Torr). Tile centre and Tile edge data are presented to realize the power coupling mechanism at different position in the multi-tile electrode discharge. It is observed that the plasma density increases monotonically with a rise in VHF power level at both positions while decreasing with an increase in the operating gas pressure. At a low gas pressure (50mTorr), plasma density profile shows a maximum at the tile centre and minimum at the tile edge position, whereas, at high gas pressures (500mTorr -- 1Torr) edge effects are observed. Measured rotational temperature ($\sim$ 350-450K) is slightly above room temperature. Vibrational temperature, measured from 6500-8000K, is increasing initially with a rise in rf power (\textless 1kW) and then saturates (above 1 kW). Similar to the plasma density profile, high vibrational temperature is measured at the tile edge compared to the tile centre. [Preview Abstract] |
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LW1.00027: Two-dimensional Simulations of a VHF H$_{2}$ Plasma for Different Discharge Gaps Kuan-Chen Chen, Kuo-Feng Chiu, Kohei Ogiwara, Li-Wen Su, Kiichiro Uchino, Yoshinobu Kawai A capacitively coupled plasma (CCP) is widely used for plasma applications. Since a tandem silicon thin film solar cells using a VHF plasma source was proposed, a study of a VHF plasma has been popular in solar cell fields. In addition, a high speed deposition of microcrystalline silicon has been achieved by a high pressure depletion method. In plasma etching, a two frequency CCP has been operated at relatively high pressures. Thus, it is important to examine the characteristics of a capacitively coupled VHF plasma at high pressures. However, a spatial distribution of the plasma parameters at a narrow gap has not been measured because of the measurement difficulty. Thus, we examined an axial distribution of the plasma parameters for different discharge gaps by the simulation using Plasma Hybrid Module. A VHF voltage (frequency: 60 MHz) was applied on parallel plate electrodes The discharge gap was varied from 8 mm to 20 mm. The electron temperature around the electrode was higher than that at the center. When the applied voltage was increased, the electron density increased while the electron temperature decreased near the center. The gap dependence of the plasma parameters was also studied. [Preview Abstract] |
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LW1.00028: INDUCTIVELY COUPLED PLASMAS |
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LW1.00029: Fluid simulation of feedstock gas transporting properties in argon inductively coupled plasmas Shu-Xia Zhao, Cheng Chen, Zhao Feng, You-Nian Wang The flow properties of feedstock gas in an argon inductively coupled plasma are investigated by compressible Navior-Stocks equation. The inlet gas flow rate and outlet fixed pressure are adjusted in their respective parameter ranges, 50-1000sccm and 20-1000mTorr. The axial symmetry and no-slip wall boundary condition are applied at the reactor axis and walls, respectively. Multi reactor configurations are derived from the realistic industry application. The results show that the gas flow velocity almost linearly increases with gas flow rate since high flow rate can result in high inlet gas velocity. The gas velocity still decreases at high outlet pressure due to the fact that the density is high at high pressure and hence the velocity drops at constant inlet mass flux density. At all considered cases, the gas is compressible, especially at the sidewall, as the gas flow rate is high and pressure is low enough. Last, the aspect ratio of reactor has significant influence on both the magnitude and profile of gas velocity. [Preview Abstract] |
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LW1.00030: Chemically active species in an Oxygen Inductively Coupled Plasma Nathaniel Ly, John Boffard, Chun Lin, Amy Wendt, Svetlana Radovanov, Harold Persing, Alexandre Likhanskii Oxygen plasmas are used in a wide variety of applications including ion implantation and photoresist striping. Here we combine non{\-}invasive optical emission spectroscopy (OES) measurements and numerical simulations to investigate the plasma parameters in both oxygen inductively coupled plasmas (ICP) and oxygen-argon ICPs. An emission model makes use of available electron impact excitation cross sections for atomic and molecular oxygen to relate measured O and O$_{\mathrm{2}}^{\mathrm{+}}$ emission intensities to corresponding plasma parameters, including the electron temperature, electron density, and the dissociation fraction of the neutral oxygen. For plasma simulations we use the CRTRS, 2D/3D code that self{\-}consistently solves for ICP power deposition, electrostatic potential and plasma dynamics in the drift{\-}diffusion approximation (or full momentum equations). Comparison of the experimental OES measurements are used to check the validity of the plasma simulation which yields results that the OES approach has difficulty in measuring including the relative fluxes of O$^{\mathrm{+}}$ and O$_{\mathrm{2}}^{\mathrm{+}}$, which is important for ion implantation. [Preview Abstract] |
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LW1.00031: Characterization of radical production mechanism in $CHF_{3} $ and $CF_{4} $ inductively coupled plasmas Yaping Wang, Shuxia Zhao Inductively coupled fluorocarbon (fc) plasmas are widely used in $Si/SiO_{2} $ etching industry as they provide active radicals which are reactive to the $Si$ or $SiO_{2}$ materials. It is well known that $CHF_{3}$ plasma has relatively low density ratio of $F$ vs. $CF_{x} $ radicals and hence high etching selectivity, as compared with the $CF_{4}$, due to the fact that one F is replaced by H in $CHF_{3}$ molecules and H can abstract F from fluorocarbon radicals to form HF. However, for now, much elaborate details are still missed in the literature. Therefore in this work, a fluid model is used to characterize the radical production components in these two different fc plasmas. The fluid model includes continuity and energy equations for electrons, continuity and momentum equations for ions and continuity equations for radicals. An electromagnetic model is used to calculate the electric field which is generate by coupling coil current and Poisson equation is used to calculate the static field within the plasma. The model predicts the electron density, ion density and radical density of $CHF_{3}$ plasma. For now the simulations of $CF_{4}$ plasma are still under construction. We expect to compare the different radical production mechanisms in the $CHF_{3} $and $CF_{4}$ plasma sources in new future. [Preview Abstract] |
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LW1.00032: Electron heating and electronegativity during E-H transition in inductively coupled RF oxygen discharge Thomas Wegner, Christian K\"ullig, J\"urgen Meichsner The E-H transition of a planar inductively coupled RF oxygen discharge was investigated using the phase resolved optical emission spectroscopy. Beside of experimental methods, an analytical calculation of the negative ion density using a particle balance equation reveals an information about the electronegativity, too. The E-mode at low RF power is characterized by RF sheath heating during the sheath expansion and the electrical field reversal which appears during the sheath collapse. The last one is a sign for high electronegativity. The axial distance of the maximum excitation rate increases due to the increasing sheath thickness. The E-H transition in this exemplary discharge is continuously and the electron heating changes smoothly. During the transition into the H-mode the capacitive and inductive heating are present and a hybrid mode is observed. Further, the electronegativity is reduced. As a result of the shrinking sheath thickness and skin depth, the axial distance of the maximum excitation rate decreases drastically. In the pure H-mode two separated patterns appear representing the electron heating for each half cycle. Due to the increases of the electron density, the skin depth drops and leads to a further decrease of the axial distance of the maximum excitation rate. [Preview Abstract] |
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LW1.00033: Experimental investigation on collisionless electron heating mechanism through electron energy probability function measurement in a low pressure inductively coupled plasma Hyun-Ju Kang, Deuk-Chul Kwon, Chin-Wook Chung Electron energy probability functions (EEPFs) were measured at various powers and frequencies in low pressure inductively coupled plasma. It is found that the EEPFs becomes flatten and the plateau region is shifted to lower energy, as driving frequency decreases or input power increases. The EEPFs with plateau energy region indicates that there is a powerful electron heating mechanism in semi-infinite discharge condition. This experimental result will be also compared to the simulation results including bounce resonance and transit time resonance heating. [Preview Abstract] |
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LW1.00034: Spatial distribution of floating potential at wafer level in inductively coupled plasmas Aixian Zhang, Ji-Hwan Park, Jin-Yong Kim, Yu-Sin Kim, Chin-Wook Chung Spatial distribution of floating potential was measured by using a wafer-type probe array. At low gas pressure, the floating potential distribution has a parabolic shape with a maximum value at the center, regardless of discharge condition. However, the floating potential distribution was remarkably changed, as the gas pressure increases in an electronegative plasma. These results are because the gas pressure changes the discharge property from nonlocal to local kinetics. Besides, negative ions can change the floating potential distribution. This study will be helpful to understand charging damage in metal oxide semiconductor manufacturing process. [Preview Abstract] |
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LW1.00035: Electron heating and control of electron energy distribution in hybrid plasma source for the enhancement of the plasma ashing processing Hyo-Chang Lee, Chin-Wook Chung In this study, control of the electron energy distribution function (EEDF) is investigated in hybrid plasma source with inductive and capacitive fields. With the addition of a small amount of antenna coil power to the capacitive discharge, low energy electrons are effectively heated and the EEDF is controlled. This method is applied to the ashing process of the photoresistor (PR). It is revealed that the ashing rate of the PR is significantly increased due to O radicals produced by the controlled EEDF, even though the ion density/energy flux is not increased. The roles of the power transfer mode, the electron heating, and the discharge parameters are also presented in the hybrid plasma source. This work can be used to an inter-ashing method during etching process. [Preview Abstract] |
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LW1.00036: Experimental investigation on collisionless heating in a finite size inductively coupled plasma Seuli Gu, Hyun-Ju Kang, Yu-Sin Kim, Yoon-Min Chang, Deuk-Chul Kwon, Chin-Wook Chung The electron energy probability functions (EEPFs) were measured in low pressure and planar-type inductively coupled plasma at various chamber heights. The plateau on the EEPFs was observed and the corresponding energy region was shifted to higher energy region with increasing chamber height. Since the electron mean free path is larger than the discharge gap length, the plateau shifting could be understood by an effect of collisionless electron heating. From calculated energy diffusion coefficient, a possible heating mechanism is the electron bounce resonance. [Preview Abstract] |
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LW1.00037: Collisionless electron heating in periodic arrays of inductively coupled plasmas Uwe Czarnetzki, Khristo Tarnev A novel mechanism of collisionless heating in large planar arrays of small inductive coils operated at radio frequencies is proposed [1]. A periodic array of multiple coils provides a well-structured, dynamic electric field which allows resonant electrons moving in the plane to gain high energies. Two types of tailored periodic structures are studied. In the ortho-array currents in all coils are in phase while in the para-array currents in adjacent coils are 180$^{\circ}$ out of phase. The concept is investigated analytically by solving the Vlasov equation and by a single particle simulation combined with Monte Carlo collisions with Argon atoms. Scaling parameters, resonances, energy exchange, and distribution functions are obtained. Analytical and numerical results are in good agreement. Pressure and electric field dependences are studied. Stochastic heating is found to be most efficient when the electron mean free path exceeds the size of a single coil cell. Then the mean energy increases approximately exponentially with the electric field amplitude. \\[4pt] [1] U. Czarnetzki and Kh. Tarnev, Physics of Plasmas \textbf{21}, 123508 (2014) [Preview Abstract] |
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LW1.00038: ABSTRACT WITHDRAWN |
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LW1.00039: Properties of large area weakly magnetized inductively coupled plasma measured by cutoff probe and tuned single Langmuir probe Eui-Jeong Son, Yong-Soo Youn, Dong-Hyun Kim, Hae June Lee, Ho-Jun Lee Applicability of cutoff probe in weakly magnetized plasmas was investigated using Drude model and electromagnetic field simulation. It was shown that the cutoff probe method can safely be used for weakly magnetized high density plasma sources. Cutoff probe system with two port network analyzer has been prepared and applied to measure electron density distributions in large area, 13.56MHz driven weakly magnetized inductively coupled plasma source. The results shown that, by applying uniform magnetic field of 12 Gauss to 5 mTorr Ar plasma, peak electron density is increased by a factor of 3 compared with non-magnetized plasma. However, radial density profile becomes more center-high and non-uniform. As the rf power increases the radial uniformity is improved. Electron temperature decreases at the chamber center and increases at the edge when the plasma is magnetized. Resulting radial temperature distribution becomes U-shape. These electron temperature profiles are well agree with self-consistent fluid simulation results. On the other hand, simulation predicted that the radial electron density distribution has M-shape, which is not agreed with experimental results. The origin of the discrepancy between simulation and experimental results are not clear. [Preview Abstract] |
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LW1.00040: MAGNETICALLY -ENHANCED PLASMAS: ECR, HELICON, MAGNETRON, OTHERS |
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LW1.00041: Low-voltage operating mode of a high-current magnetized cold-cathode plasma Timothy Sommerer, Steven Aceto, David Smith, Nicholas Hitchon, James Lawler A series of approximations and simple models is used to estimate the properties of a cold-cathode plasma in a high-voltage, high-power gas switch for use in grid-scale electric power conversion. The active plasma volume is a plane-parallel gap $\approx$1 cm filled with helium at a pressure on order 0.1 torr. A magnetic field in the region adjacent to the cathode is used to increase the current density to practical levels $>$1 A/cm$^2$. The plasma can operate in a ``low voltage mode'' ($\approx$80 V) that has the appearance of a constricted attachment at the cathode surface and a more diffuse region toward the anode. Cathode material is absent from the plasma emission spectrum. Various attempts to model the spot indicate that the plasma in the constriction is near full ionization, and that there is a dynamic balance of neutral gas atoms between the constriction, the cathode surface, and the neighboring diffuse plasma. The electron emission mechanism is assumed to be conventional, by ion impact, but field emission may contribute. [Preview Abstract] |
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LW1.00042: Non-diffusive perpendicular transport of strongly magnetized plasma Min-Keun Bae, Richard Pitts, Jun Gyo Bak, Suk-Ho Hong, Heong Su Kim, Kyu-Sun Chung Characteristics of high energy particles spilled out from magnetically confined plasma reaching the wall are measured by electric probes. Energetic plasma bursts, called filament, during the edge localized mode(ELM) of fusion device are non-diffusively moving to the wall, which is perpendicular to the magnetic field(B$_{\mathrm{t}} = $ 1 $\sim$ 3 T). These intermittent ELM filaments can carry significant particle and heat to the first wall. Poloidal probes which are composed of two triple probes(TPs) and one Mach probe(MP) installed at first wall of Korea Superconducting Tokamak Advanced Research(KSTAR) device. These probes are located 2398mm from the machine center and 74mm behind the poloidal limiter. Poloidal probes are used as a triple probe and measured ion saturation current and floating potential with 200 kHz. From the direct measurement of electron temperature, ion saturation currents(TP) and Mach numbers(MP), relevant plasma parameters such as heat flux, three dimensional flow velocities, and plasma density have been deduced. [Preview Abstract] |
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LW1.00043: Origin of Substrate Heating During Oxide Film Deposition by DC Magnetron Discharge and Superposition of VHF Power Kenta Setaka, Takashi Fukui, Kensuke Sasai, Hirotaka Toyoda Magnetron plasmas are one of the important tools for thin film deposition such as metal, oxides and so on. In general, quality of sputter deposited film is influenced by substrate temperatures and this implies that the discharge condition is strongly related to the film quality. In this study, substrate temperature is measured in a DC magnetron plasma with VHF power superposition and origin of substrate heating is investigated. In the experiment, ITO films are deposited by a DC magnetron sputter source to which VHF power is superposed. Substrate temperature is measured as a function of VHF power fraction with respect to total discharge power, i.e., DC and VHF powers. The substrate temperature shows the minimum at VHF power fraction of $\sim$ 60{\%}. From Langmuir probe measurement and laser absorption spectroscopy, both plasma density and gas temperature monotonically increases with the VHF fraction, which explains the substrate temperature increase at high VHF power fractions. However, the temperature increase at low VHF power fraction cannot be explained by heat flux by ions or discharge gas. Contribution of negative ion impingement to the substrate is considered to be the origin of the substrate temperature at low VHF power fractions or conventional DC sputter depositions. [Preview Abstract] |
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LW1.00044: Production of fast plasma flows with a steady state high density plasma in TPD-SheetIV Takaaki Iijima, Yuta Tanaka, Takuya Hase, Toshikio Takimoto, Akira Tonegawa, Kohnosuke Sato, Kazutaka Kawamura Ion acceleration of high density sheet plasma (ca.10$^{18}$m$^{-3}$) in a non-uniform magnetic field by ion-cyclotron resonance (ICR) is investigated in a linear plasma device, TPD-Sheet IV. The radio frequency (RF) electrodes consist of two parallel plates. The ion energy along the axis of the magnetic field or in the perpendicular direction was measured using a Faraday cup. The experiment was conducted using helium gas and a discharge current of 50 A. The ion energy in the direction perpendicular to the magnetic field line increases by ion-cyclotron resonance. Ions are also accelerated along the axis of the magnetic field line due to the magnetic field gradient along the axis. [Preview Abstract] |
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LW1.00045: Modeling of the Reactive High Power Impulse Magnetron Sputtering (HiPIMS) process Jon Tomas Gudmundsson, Daniel Lundin, Michael Raadu, Nils Brenning, Tiberiu Minea Reactive high power impulse magnetron sputtering (HiPIMS) [1] provides both a high ionization fraction of the sputtered material and a high dissociation fraction of the molecular gas. We demonstrate this through an ionization region model (IRM) [2] of the reactive Ar/O$_2$ HiPIMS discharge with a titanium target. We explore the influence of oxygen dilution on the discharge properties such as electron density, the ionization fraction of the sputtered vapor and the oxygen dissociation fraction. We discuss the important processes and challenges for more detailed modeling of the reactive HiPIMS discharge. Furthermore, we discuss experimental observations during reactive high power impulse magnetron sputtering sputtering (HiPIMS) of Ti target in Ar/N$_2$ and Ar/O$_2$ atmosphere. The discharge current waveform is highly dependent on the reactive gas flow rate, pulse repetition frequency and discharge voltage. The discharge current increases with decreasing repetition frequency and increasing flowrate of the reactive gas [3].\\[4pt] [1] J. T. Gudmundsson et al. J. Vac. Sci. Technol. A, 30 (2012) 030801\\[0pt] [2] M. A. Raadu et al. Plasma Sources Sci. Technol. 20 (2011) 065007\\[0pt] [3] F. Magnus et al. J. Vac. Sci. Technol., 30 (2012) 050601 [Preview Abstract] |
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LW1.00046: Measurements of steady-state radial cross-field ion flows in a helicon plasma Derek Thompson, Earl Scime, M. Umair Siddiqui Radial ion drift velocity, electron temperature, plasma potential, and density profiles in front of a grounded boundary plate were obtained in a helicon plasma for $\rho_{\mathrm{i}}$/$\lambda $ ranging from 0.34 to 1.6, in order to directly investigate the effects of ion-neutral collisions on cross field transport. Measurements indicate that such simple scalings do not rigorously predict the behavior of cross-field drift profiles in the presence of simple complications such as multi-dimensional flows. Results are compared to basic fluid models in order to gain further insight on possible complications affecting cross-field transport. [Preview Abstract] |
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LW1.00047: HIGH PRESSURE DISCHARGES: DIELECTRIC BARRIER, DISCHARGES, CORONAS, BREAKDOWN, SPARKS |
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LW1.00048: The breakdown process in an atmospheric pressure nanosecond parallel-plate discharge Yi-Kang Pu, Bang-Dou Huang, Keisuke Takashima, Xi-Ming Zhu The breakdown process in an atmospheric pressure nanosecond discharge with parallel-plate electrodes is investigated by temporally and spatially resolved optical emission spectroscopy (OES). The electric field is obtained from the Stark splitting of the He I 492.1 nm line. From the line ratio and a collisional-radiative model, the Te, high and Te, low (representing the effective Te in the high energy and low energy part of the EEDF, respectively) are obtained. It is found that during the breakdown process the electric field is enhanced at the ionization wave front, while it is weakened behind the wave front. This spatial profile of the electric field strongly correlates with that of both the Te, high and Te, low. The Te, high is much larger than the Te, low, which indicates that an elevated high energy tail in the EEDF is being built up under the strong electric field during the breakdown process. This argument is supported by the result from a Monte-Carlo simulation. [Preview Abstract] |
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LW1.00049: ROS/RNS Production in Water Using Various Discharge Plasma Kazuhiro Takahashi, Kohki Satoh, Hidenori Itoh, Hideki Kawaguchi, Igor Timoshkin, Martin Given, Scott MacGregor A pulsed discharge, a DC corona discharge and an atmospheric pressure plasma jet are generated above water, the off-gas of a packed-bed dielectric barrier discharge (PB-DBD) is sparged into water, and then reactive oxygen species and reactive nitrogen species in the water are investigated. H$_{2}$O$_{2}$, NO$_{3}^{-}$ and a trace of NO$_{2}^{-}$ are produced in the water after the plasma exposure. H$_{2}$O$_{2}$ concentration decreases when NO$_{3}^{-}$ concentration increases, so that this is likely that OH radical to produce H$_{2}$O$_{2}$ by OH $+$ OH $\to $ H$_{2}$O$_{2}$ is consumed in the NO$_{3}^{-}$ production by NO$_{2} \quad +$ OH $\to $ HNO$_{3} \to $ NO$_{3}^{-} \quad +$ H$^{+}$ (in water). Since no species is detected in water by the sparging of the PB-DBD off-gas containing more than 1000 ppm of O$_{3}$, O$_{3}$ does not contribute to produce H$_{2}$O$_{2}$ in water. Further, only NO$_{3}^{-}$ is produced by the sparging of the off-gas containing N$_{2}$O$_{5}$ and HNO$_{3}$. This leads that H$_{2}$O$_{2}$ and NO$_{2}^{-}$ can be produced by short-lifetime species in plasma. In this work, the highest generation efficiency of H$_{2}$O$_{2}$ and NO$_{2}^{-}$ are respectively 3,820 $\mu $g/Wh and 830 $\mu $g/Wh by the pulsed-plasma exposure, and that of NO$_{3}^{-}$ is 2,530 $\mu $g/Wh by the off-gas sparging of the PB-DBD. [Preview Abstract] |
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LW1.00050: Numerical Study of Breakdown Pattern Induced by Intense Microwave under Atmospheric Conditions Masayuki Takahashi, Ohnishi Naofumi Breakdown experiment using intense microwaves was conducted under atmospheric pressure, and plasma arrays were observed in nitrogen. However, in helium breakdown, the breakdown pattern is different from that of nitrogen. Discrete plasma pattern was obtained in the downstream region of the plasma propagation. On the other hand, the upstream region shows a diffusive plasma pattern in the helium breakdown. Propagation speed of the plasma front has dependencies on chemical species; however, organized discussion of the breakdown process was not conducted for several chemical species. We simulate the microwave discharge process for nitrogen, helium, and hydrogen using a one-dimensional fluid modeling to examine dependencies of the breakdown structure on chemical species. Plasma arrays are obtained in nitrogen and hydrogen because the electron diffusion is smaller than that of helium. On the other hand, the diffusive pattern is reproduced in helium because the electron diffusion is larger. The propagation speed of the helium breakdown is larger than that of nitrogen and hydrogen because of larger diffusion and larger ionization. We will discuss that dependencies of the breakdown process on chemical species based on a multi-dimensional fluid model in the full paper. [Preview Abstract] |
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LW1.00051: Chemical Kinetics Reduction of High Pressure Non-Equilibrium Plasma Discharges in Complex Gases Using Principal Component Analysis Ashish Sharma, Laxminarayan L. Raja Kinetic models of plasma discharge in complex gases involve solving the continuity equation for each reaction for updation of species at each time step. The number of reactions, especially in complex gases like methane, can be really large and thus, this approach is computationally expensive. It also makes the system very stiff due to orders of magnitude difference in rate constants. Principal Component Analysis (PCA) is technique which allows the identification of significant variables governing the course of a chemical kinetics model. This allows us to describe its behavior in a lower dimensional space with lesser variables and reduction is obtained since kinetic reactions only need to be solved for these principal components and not for all the species in the plasma discharge model. The non-linear nature of the source terms in plasma discharges also makes the traditional PCA technique less effective. In the current work an attempt has been made to develop an approach for reduction of chemical kinetics of non-equilibrium plasma discharges in methane gas at atmospheric pressure using PCA. The approach also explores the use of linear and non-linear source term reconstruction techniques for effective projection of source terms back to the higher dimensional space. [Preview Abstract] |
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LW1.00052: Timing Control of Self-organized Dielectric Barrier Discharge and Influence of Discharge Driving Frequency Junichi Sugawara, Yuki Kubota, Hidenori Oki, Seiji Mukaigawa, Koichi Takaki The two-dimensional array of filaments generated by the self-organizing of atmospheric dielectric-barrier discharges has plasma photonic crystal applications. The net generation time for the self-organization of discharge in one cycle is expected to be short because of its self-extinguishing feature, but that did not happen. However, we attempted to shorten the net generation time by implementing a time difference to drive the parallel array discharge units. The timing of the voltage applied to the discharge cells was controlled by the metal-oxide-semiconductor field-effect-transistors of the circuits, which were turned on by a signal from a single peripheral interface controller. The resultant duty cycles of the discharge current duration per cycle were 6{\%} (single cell), 12{\%} (two parallel cells), and 27{\%} (three parallel cells). When the frequency was changed from 100 to 300 kHz, the generation time increased from 0.61 to 0.72 $\mu $s (100 kHz), 0.91 to 1.23 $\mu $s (200 kHz), and 1.54 to 1.91 $\mu $s (300 kHz). According to these results, frequency and maintenance time are proportional. [Preview Abstract] |
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LW1.00053: Generation of atmospheric micro gap radio-frequency discharge plasma under controlled temperature conditions Takumi Araya, Takashi Shibata, Hiroki Kikuchi, Seiji Mukaigawa, Koichi Takaki In dielectric barrier discharge, determining the temperature of a dielectric barrier is difficult owing to a rise in the temperature of a barrier and an electrode because heat generated in a discharge space exhibits a complex local distribution involving gas flow and heat transfer structures. In this study, we examined the effect of dielectric barrier temperature on plasma characteristics and a two-dimensional spatial distribution of the discharge in a radio-frequency atmospheric-pressure plasma. The temperature of the dielectric barrier was kept between 10 $^{\circ}$C and 50 $^{\circ}$C by circulating hot or cold water in a flow channel in a lower grounded electrode using a cooling water circulating device. Breakdown voltage tended to decrease with an increase in the temperature of the barrier. Depending on an increase in the applied voltage, the discharge aspect was observed to shift to the discharge having two regions, i.e., the bright and dark regions. The area of the bright region increased with an increase in the applied voltage and dielectric barrier temperature. In addition, the current density of the bright region was very high compared with that of the dark region, and therefore, the bright and dark regions were in the glow and Townsend-like modes, respectively. [Preview Abstract] |
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LW1.00054: Experiment and modeling of laser photodetachment of negative ions in helium oxygen barrier discharges Robert Tschiersch, Sebastian Nemschokmichal, J\"urgen Meichsner Helium oxygen discharges operating at atmospheric pressure are of great interest for applications, such as surface treatment of biological samples. Helium as the buffer gas keeps the driving power low, and oxygen serves as the source of radicals. The large electronegativity of oxygen results in the formation of negative ions which in turn have a remarkable influence on the discharge development. To point out this role of negative ions, the change of the discharge behavior after the laser photodetachment of negative ions is measured in a helium oxygen barrier discharge. These measurements reveal a lower breakdown voltage when firing the laser during the pre-phase of the discharge. The reason is the additional pre-ionization by the detached electrons which was proved by an 1D numeric fluid modeling. The next step is the determination of absolute number densities of negative ions by a comparison of the experimental parameter variations with those from the modeling. Furthermore, the actual role of negative ions on the discharge behavior will be emphasized by the modeling. [Preview Abstract] |
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LW1.00055: Field-emitting Townsend regime of surface dielectric barrier discharges generated in CO$_{2}$ emerging at high pressure David Pai, Sven Stauss, Kazuo Terashima Surface dielectric barrier discharges (DBDs) in CO$_{2}$ from atmospheric pressure up to supercritical conditions ($T_{c} = $ 304.13 K, $p_{c} =$7.4 MPa) generated using 10-kHz ac excitation are studied experimentally. Two discharge regimes are obtained: the standard and field-emitting Townsend regimes. The former resembles typical surface DBDs that have streamer-like characteristics, but the latter has not been reported previously. Here we present an analysis of the electrical and optical diagnostics of the field-emitting Townsend discharge regime using current-voltage and charge-voltage measurements, imaging, optical emission spectroscopy, and spontaneous Raman spectroscopy. Using an electrical model, it is possible to calculate the discharge-induced capacitances of the plasma and the dielectric, as well as the space-averaged values of the surface potential and the potential drop across the discharge. The model also accounts for the space-averaged Laplacian field by including the capacitance due to the fringe electric field from the electrode edge. The electrical characteristics are similar to those of atmospheric-pressure Townsend DBDs, i.e. self-sustained DBDs with minimal space-charge effects. The purely continuum emission spectrum is due to electron-neutral bremsstrahlung, with a corresponding average electron temperature of 2600 K. Raman spectra of CO$_{2}$ near the critical point demonstrate that the discharge increases the average gas temperature by less than 1 K. [Preview Abstract] |
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LW1.00056: Influence of surface processes on surface discharges generated on borosilicate glass barriers in high-pressure CO$_{2}$ up to supercritical conditions David Pai, Sven Stauss, Kazuo Terashima Surface dielectric barrier discharges (DBDs) generated in CO$_{2}$ from atmospheric pressure up to supercritical conditions ($T_{c} = $ 304.13 K, $p_{c} = $ 7.4 MPa) using 10-kHz AC excitation are investigated experimentally using current-voltage and charge-voltage measurements, imaging, and optical emission spectroscopy. Surface processes are investigated to resolve unexplained phenomena from related work on the ``standard'' and ``field-emitting Townsend'' discharge regimes. Variations in the energy, residual or ``memory'' charge, and spatial homogeneity of the field-emitting Townsend regime are shown to depend on the duration that the discharge runs continuously. The memory charge is positive for the field-emitting Townsend regime but negative for the standard regime. It is demonstrated that high discharge homogeneity and low variation in the discharge energy is correlated with the maximization of positive memory charge. Charge neutralization of plasma ions and electrons by anions and cations in the borosilicate glass is proposed as the process responsible for the presence of nanosecond current pulses in the field-emitting Townsend regime. [Preview Abstract] |
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LW1.00057: Ozone production using dielectric barrier discharge in oxygen and carbon dioxide Francisco Pontiga, Roukia Abidat, Helena Moreno, Fern\'andez-Rueda Agust\'in, Saida Rebia\"i The generation of ozone in oxygen and carbon dioxide using a planar dielectric barrier discharge (DBD) has been experimentally investigated. The DBD reactor was operated at moderate voltages (4.2 to 5.6 kV) and frequencies (50 to 500 Hz) and the gas flow rate was varied in the range 50 to 200 cm$^{3}$/min. The averaged consumed power (\textless 1 W) was evaluated using a monitor capacitor of known capacitance (1$\mu$F). The effluent gas from the DBD reactor was diverted to a gas cell situated inside the sample compartment of a UV spectrophotometer. Therefore, ozone concentration was determined from the measurement of absorbance using Beer-Lambert law. The results have shown that ozone concentration in oxygen grows very linearly with the input power. In contrast, the production of ozone in carbon dioxide is less regular, which may be due to the deposition of a thin layer over the stainless steel electrode during the application of the electrical discharge. Moreover, the rate of ozone production with the injected energy density was found to be 500 times weaker in carbon dioxide than in pure oxygen. [Preview Abstract] |
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LW1.00058: Discharge characteristics and hydrodynamics behaviors of atmospheric plasma jets produced in various gas flow patterns Yuichi Setsuhara, Giichiro Uchida, Atsushi Nakajima, Kosuke Takenaka, Kazunori Koga, Masaharu Shiratani Atmospheric nonequilibrium plasma jets have been widely employed in biomedical applications. For biomedical applications, it is an important issue to understand the complicated mechanism of interaction of the plasma jet with liquid. In this study, we present analysis of the discharge characteristics of a plasma jet impinging onto the liquid surface under various gas flow patterns such as laminar and turbulence flows. For this purpose, we analyzed gas flow patters by using a Schlieren gas-flow imaging system in detail The plasma jet impinging into the liquid surface expands along the liquid surface. The diameter of the expanded plasma increases with gas flow rate, which is well explained by an increase in the diameter of the laminar gas-flow channel. When the gas flow rate is further increased, the gas flow mode transits from laminar to turbulence in the gas flow channel, which leads to the shortening of the plasm-jet length. Our experiment demonstrated that the gas flow patterns strongly affect the discharge characteristics in the plasma-jet system. [Preview Abstract] |
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LW1.00059: Streamer development in barrier discharge in air: spectral signatures and electric field Tomas Hoder, Milan Simek, Zdenek Bonaventura, Vaclav Prukner Electrical breakdown in the upper atmosphere takes form of so called Transient Luminous Events (TLE). Down to the certain pressure limit, the first phases of the TLE-phenomena are controlled by the streamer mechanism. In order to understand the development of these events, streamers in 10 torr air were generated in volume barrier discharge. Stability and reproducibility of generated streamers were secured by proper electrode geometry and specific applied voltage waveform. In this work, spectrally resolved measurements of the streamer head emission with high spatial and temporal resolution are presented. Precise recordings of the emission of the second positive and first negative systems of molecular nitrogen allowed the determination of the spatio-temporal development of the reduced electric field in the streamer head. This unique experimental result reveals in more details the early stages of the streamer development and gives, besides values for streamer velocity and its diameter, quantitative information on the magnitude of the electric field. [Preview Abstract] |
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LW1.00060: PIC-DSMC analysis on interaction of a laser induced discharge and shock wave Kohei Shimamura Laser induced discharge and the shock wave have attracted great interest for use in the electrical engineering. When the high intensity laser (10 GW \textgreater ) is focused in the atmosphere, the breakdown occurs and the discharge wave propagates toward to the laser irradiation. The shock wave is generated around the discharge wave, which is called as the laser supported detonation wave. After breakdown occurred, the initial electron of the avalanche ionization is produced by the photoionization due to the plasma radiation. It is well recognized that the radiation of the laser plasma affects the propagation mechanism of the laser induced discharge wave after the initiation of the breakdown.$^{\mathrm{\thinspace }}$However, it is difficult to observe the interaction between the plasma radiation and the electron avalanche in the ionization-wave front in experimentally except in the high intensity laser. In the numerical calculation of the laser-induced discharge, the fluid dynamics based on the Navier-Stokes equation have been widely used. However, it is difficult to investigate the avalanche ionization at the wave front using the fluid dynamics simulation. To investigate the interaction of the ionization-wave front and the shock wave, it is appropriate to utilize the PIC-DSMC method. The present study showed the propagation of the ionization front of the discharge wave and the shock wave using the particle simulation. [Preview Abstract] |
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LW1.00061: Streamer properties in a repetitively pulsed plasma jet from 1 to 100 kHz Brian Sands, Biswa Ganguly, James Scofield We investigate the properties of guided streamers in a nanosecond repetitively pulsed dielectric barrier plasma jet at repetition rates up to 100 kHz. In this regime, remnant ionization and neutral metastable concentrations are significant in the channel through which the streamer propagates. Both helium and a Penning mixture of helium and argon are investigated as feed gases for a plasma jet in a controlled pressure chamber with a flowing nitrogen background. The applied voltage pulse was set at 8 kV, with a risetime of 15 ns and falltime of 8.5 $\mu$s. Streamer dynamics were monitored using spatiotemporally-resolved emission spectroscopy with a PMT filtered at 706.5 nm He (3$^3$S - 2$^3$P) and 587.6 nm He (3$^3$D - 2$^3$P) to track the streamer head. Temporally-resolved ICCD imaging was also used to characterize discharge development. Tunable diode laser absorption spectroscopy was used to measure He (2$^3$S$_1$) and Ar ($^3$P$_2$) metastable densities in the streamer channel, and streamer current was measured using an inductive current monitor. As the pulse rate is increased, the streamer dynamics are significantly altered, while production of He (2$^3$S$_1$) and Ar ($^3$P$_2$) is enhanced with alternate production channels becoming important in the case of He (2$^3$S$_1$). [Preview Abstract] |
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LW1.00062: Influence of dielectric materials on radial uniformity in non-equilibrium atmospheric pressure helium plasma Akinori Oda, Kyohei Komori Non-equilibrium atmospheric pressure plasma has been utilized for various technological applications such as surface treatment, materials processing, bio-medical and bio-logical applications. For optimum control of the plasma for the above applications, numerous experimental and theoretical investigations on the plasma have been reported. Especially, controlling radial uniformity of the plasma are very important for utilizing materials processing. In this paper, an axially-symmetric three-dimensional fluid model, which is composed of the continuity equation for charged and neutral species, the Poisson equation, and the energy conservation equation for electrons, of non-equilibrium atmospheric pressure helium plasma has been developed. Then, influence of dielectric properties (e.g. relative permittivity, secondary electron emission coefficient, etc.) of dielectric materials on radial plasma uniformity (i.e. radial distributions of electron density, ion density, electric field in the plasma) was examined. [Preview Abstract] |
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LW1.00063: High Power Helicon Plasma Source for Plasma Processing James Prager, Timothy Ziemba, Kenneth E. Miller Eagle Harbor Technologies (EHT), Inc. is developing a high power helicon plasma source. The high power nature and pulsed neutral gas make this source unique compared to traditional helicon source. These properties produce a plasma flow along the magnetic field lines, and therefore allow the source to be decoupled from the reaction chamber. Neutral gas can be injected downstream, which allows for precision control of the ion-neutral ratio at the surface of the sample. Although operated at high power, the source has demonstrated very low impurity production. This source has applications to nanoparticle productions, surface modification, and ionized physical vapor deposition. [Preview Abstract] |
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LW1.00064: Spectroscopic Investigation of a Dielectric Barrier Discharge Over a Wide Range of Pulse Parameters Julian Picard, James Prager, Timothy Ziemba, Kenneth E. Miller, Akel Hashim Most high voltage pulser used to drive dielectric barrier discharges (DBDs), produce a single pulse shape (width and voltage), thus making it challenging to assess the effect of pulse shape on the production of different chemical species during a discharge. Eagle Harbor Technologies (EHT), Inc. has developed a nanosecond pulser that allows for independent control of the output voltage, pulse width, and pulse repetition frequency. Through the utilization of this technology, presented here is a precise characterization of reactive species generated by the DBD under the independent variation of voltage (0-20 kV), frequency (0-20 kHz) and pulse width (20-260 ns). A better understanding of this parameter dependency can allow for more targeted and effective application of plasma in medical, environmental, industrial, and other applications. [Preview Abstract] |
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LW1.00065: Surface treatment of a titanium implant using low temperature atmospheric pressure plasmas Hyun-Young Lee, Tianyu Tang, Jung-Woo Ok, Dong-Hyun Kim, Ho-Jun Lee, Hae June Lee During the last two decades, atmospheric pressure plasmas(APP) are widely used in diverse fields of biomedical applications, reduction of pollutants, and surface treatment of materials. Applications of APP to titanium surface of dental implants is steadily increasing as it renders surfaces wettability and modifies the oxide layer of titanium that hinders the interaction with cells and proteins. In this study, we have treated the titanium surfaces of screw-shaped implant samples using a plasma jet which is composed of a ceramic coaxial tube of dielectrics, a stainless steel inner electrode, and a coper tube outer electrode. The plasma ignition occurred with Ar gas flow between two coaxial metal electrodes and a sinusoidal bias voltage of 3 kV with a frequency of 20 kHz. Titanium materials used in this study are screw-shaped implants of which diameter and length are 5 mm and 13 mm, respectively. Samples were mounted at a distance of 5 mm below the plasma source, and the plasma treatment time was set to 3 min. The wettability of titanium surface was measured by the moving speed of water on its surface, which is enhanced by plasma treatment. The surface roughness was also measured by atomic force microscopy. The optimal condition for wettability change is discussed. [Preview Abstract] |
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LW1.00066: Laser diagnostics on atmospheric-pressure low-temperature helium pulsed plasmas in room- and cryogenic-temperature environments Noritaka Sakakibara, Hitoshi Muneoka, Keiichiro Urabe, Ryoma Yasui, Kazuo Terashima In atmospheric-pressure low- temperature plasmas, the control of the plasma gas temperature ($T_{\mathrm{g}})$ by a few kelvin is considered to be crucial for their applications to novel materials processing such as bio-materials. However, there have been only few studies that focused on the influence of $T_{\mathrm{g}}$ on the plasma characteristics. On the other hand, it was reported that helium metastables played a key role in the dependency of chemical reactions on $T_{\mathrm{g}}$ in helium-nitrogen plasmas. In this study, laser diagnostics were carried out in atmospheric-pressure helium pulsed plasmas near or below room temperature, at 340$-$100 K. Parallel electrodes of copper rods (diameter: 2~mm) with a gap distance of 535~$\mu$m were used and pulsed discharges with a pulse width of a few hundred nanoseconds were generated inside a reactor. The density and lifetime of helium metastables were estimated by laser absorption spectroscopy measurements and $T_{\mathrm{g}}$ was evaluated by near-infrared laser heterodyne interferometry measurements. At 300~K, the helium metastable density was 1.5 $\times$ 10$^{13}$ cm$^{-3}$ while the lifetime was 3.1~$\mu$s, and increase in $T_{\mathrm{g}}$ was up to 70~K. Dependency of the density and lifetime of helium metastables on $T_{\mathrm{g}}$ was observed and also discussed. [Preview Abstract] |
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LW1.00067: Effect of the Discharge Voltage on the Performance of the Hall Thruster Ping Duan, An-Ning Cao, Guang-Rui Liu, Xing-Yu Bian, Yan Yin, Long Chen A two-dimensional physical model is established according to the discharging process in the Hall thruster discharge channel. By using particle-in-cell method, the influences of the discharge voltage on the distribution of the potential, ion number density, electron temperature and ion radial velocity are investigated in a fixed magnetic field configuration, and the reason of discharge current increasement along with discharge voltage is also analyzed. It is found that, while the discharge voltage increases during 250-650V, the distribution of electric potential has a small expansion towards anode in axis direction, the ion radial velocity at the exit is reduced, and collision frequency between ions and wall surface is also decreased. Meanwhile, the saturation of electron temperature is observed when discharge voltage is in the range of 400-450V, and the electron temperature decreases. When the discharge voltage increases to 700V, the distribution of potential expands towards anode in axis direction significantly, the acceleration region length is greatly increased, the ionization region is compressed to the vicinity of anode, the ion radial velocity near the wall increases and collision frequency between ions and wall surface is enhanced. As the increasement of near wall conductive current and high energy electron number inside the discharge channel, the discharge current increases monotonously with the increase of discharge voltage. [Preview Abstract] |
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LW1.00068: MICRODISCHARGES, DC, RF, MICROWAVE |
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LW1.00069: Microplasma deposition of challenging thin films at atmospheric pressure Jeffrey Hopwood, H.C. Thejaswini Non-equilibrium microplasmas produce fluxes of ions and excited species to a surface while maintaining the surface near room temperature. At atmospheric pressure, however, it is very difficult to accelerate the highly collisional ions. While many applications do not benefit from energetic interactions between plasma and surface, conventional plasma deposition of thin films often requires either ion bombardment or substrate heating. For example, diamondlike carbon (DLC) is known to require $\sim$ 100 eV ion bombardment and transparent conducting oxides (TCO) typically require substrate temperatures on the order of 400-500 K. A microwave-induced microplasma is used to dissociate dilute precursor molecules within flowing helium. The precursor and plasma species result in rapid deposition of thin films (\textgreater 1 $\mu$m/min). This plasma produces a steady-state ion flux of 6x10$^{17}$ cm$^{-2}$s$^{-1}$, which is more than two orders of magnitude greater than a low pressure capacitively coupled plasma. Likewise, the metastable density is roughly two orders greater. These and other microplasma diagnostics are correlated with the measured film properties of microplasma-deposited DLC and TCO. This study shows that high ion flux, even at low energy ($\sim$ 1 eV), can provide the needed surface interactions to produce these materials at room temperature. [Preview Abstract] |
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LW1.00070: Breakdown of atmospheric pressure microgaps at high excitation frequencies Dmitry Levko, Laxminarayan Raja Microwave breakdown of atmospheric pressure microgaps was studied by a one-dimensional Particle-in-Cell Monte Carlo Collisions numerical model. The effect of both field electron emission and secondary electron emission (due to electron impact, ion impact, and primary electron reflection) from surfaces on the breakdown process is considered. For conditions where field emission is the dominant electron emission mechanism from the electrode surfaces, it is found that the breakdown voltage of mw microdischarge coincides with the breakdown voltage of direct-current microdischarge. When microdischarge properties are controlled by both field and secondary electron emission, breakdown voltage of mw microdischarge exceeds that of dc microdischarge. When microdischarge is controlled only by secondary electron emission, breakdown voltage of mw microdischarge is smaller than that of dc microdischarge. It is shown that if the interelectrode gap exceeds some critical value, mw microdischarge can be ignited only by electrons initially seeded within the gap volume. In addition, the influence of electron reflection and secondary emission due to electron impact is studied. [Preview Abstract] |
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LW1.00071: Study of microplasmas from GHz to THz Jos\'{e} Greg\'{o}rio, Alan R. Hoskinson, Stephen Parsons, Jeffrey Hopwood We present a study of atmospheric-pressure microplasmas sustained from 0.5 GHz to 0.5 THz with continuous excitation frequencies. A fluid model shows the existence of electron plasma resonances in a highly collisional microplasma. At 0.5 GHz the behavior is similar to a typical rf collisional discharge. As frequency increases at constant power density we observe a decrease in the discharge voltage from greater than 100 volts to less than 10 volts. This minimum voltage amplitude is attained when electron temporal inertia delays the discharge current to be in phase with the applied voltage. Above this frequency the plasma develops resonant regions where the excitation frequency equals the local plasma frequency. In these volumes the instantaneous quasi-neutrality is perturbed and intense internal currents emerge ensuring a low voltage operation range. This enhanced plasma heating mechanism vanishes when the excitation frequency is larger than the local plasma frequency everywhere in the plasma volume. For a typical peak electron density of $5\times10^{20}$ m$^{-3}$ this condition corresponds to $\sim$ 0.2 THz. [Preview Abstract] |
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LW1.00072: Spaceresolved determination the features and parameters of plasmoids obtained by gyromagnetic autoresonance. Denis Chuprov, Victor Andreev, Anatoliy Umnov, Andrey Novitskii Experiment and computer simulation with relativistic plasma obtained under gyromagnetic autoresonance (GA) condition are described. X-ray spectrometry, radiometry and imaging methods were applied to investigate obtained plasmoids. Energies of measured bremsstrahlung spectrums up to 0,5 MeV were observed. Investigation of the spatial anisotropy of produced X-ray radiation gave information about the plasmoid shape, localization and movement. The complex motion of the belt shaped relativistic plasmoid can be presented as rotation of the driving center around trap symmetry axis. Obtained experimental results are in good quantitative agreement with numerical simulations of GA process by particles-in-cell model. [Preview Abstract] |
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LW1.00073: Scaling of Small Arrays of Microplasmas Chenhui Qu, Peng Tian, Mark J. Kushner Arrays of microplasmas have meta-material capabilities that enable altering the properties of incident electromagnetic waves. The desirable properties of these microplasma arrays (MPAs) are high plasma density, rapid re-configuration and a minimum of isolating structures between microplasma elements that might perturb the dielectric properties of the array. These attributes are in part achieved by tradeoffs between gas mixture, pressure and pulse-power waveform. In this paper, results from a computational investigation of MPAs sustained in rare gas mixtures will be discussed. A 2-dimensional plasma hydrodynamics model with radiation transport was used to investigate the ability to modulate the permittivity of small MPAs -- up to 4 x 4 elements. Gas pressures are tens to hundreds of Torr in mixtures of rare gases (e.g., Ar/Xe). We found that in the absence of isolating structures, there is significant cross talk between the elements of the MPAs when using repetitive uni- and bi-polar pulses (tens to hundreds ns duration). For example, when alternate elements of the array are pulsed, unpowered electrodes of adjacent pixels may appear cathodic or anodic to its neighbors, thereby attracting current through the unpowered pixel. [Preview Abstract] |
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LW1.00074: Effect of external floating electrode for enhancing efficiency of generating an atmospheric pressure inductively coupled microplasma Katsuki Tukasaki, Shinya Kumagai, Minoru Sasaki To make a plasma source which can generate a microplasma at low power without using an ignitor (ex. high-voltage power supply), we have used an electrically floating electrode inside a glass tube surrounded by an antenna coil of inductive coupling [1]. Helium gas was fed into the glass tube. When VHF power was supplied to the antenna coil, the floating electrode reached electrically high potential and an atmospheric pressure inductively coupled microplasma was generated. The ignition power depended on the length of the floating electrode further. The longer the length was, the less ignition power was. To make the plasma source compact, the floating electrode was moved outside the glass tube (O.D. 1.5mm, I.D. 1mm) while only a part of floating electrode (Ni wire, 10mm, $\phi $0.3mm) was remained inside the glass tube. Both the cable and Ni wire was magnetically connected to each other through the wall of glass tube. With changing the cable length, ignition power was measured. The ignition power varied with the unit of half wavelength of the VHF. The wavelength resonance effect decreased the ignition power.\\[4pt] [1] Asano et al., Jpn. J. Appl. Phys. 51, 011AA01, 2012. [Preview Abstract] |
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LW1.00075: Design and Use of a Microdischarge of Argon in a Liquids Gerardo Ruiz Vargas, Antonio Ju\'arez Reyes We have designed and implemented a pulsed micro-plasma of Argon with a liquid electrode. The system allows to detect metallic compounds dissolved in water. The microplasma is used as a source of excitation source and the discharge operates at atmospheric pressure according to the Paschen law. Coupling a CCD monochromator of our design to the microplasma source with liquid electrode, we are able to carry out emission spectroscopy of the excited species present in the sample. For the proof of concept test of this instrument we used a dissolved solution, in the milli-mol range of HgCl$_{2}$ which is one of the water soluble forms of mercury. This experimental setup is able to detect lower concentrations of Hg in the range of 10mili-mol. This device is designed to be placed on a sample of water and perform in situ measurement. We design a chamber in which the micro-electrodes are connected to a ventury. The pressure drop in the ventury is achieved with the flow of Argon. With this arrange it is possible to carry the water from a container to inside de chamber into the space between two electrodes. One of these electrodes is submerged in water (liquid electrode) and the other exposed to Argon. Mercury has very intense peaks in 253.65nm and 435.8nm, and less intense in 365.01nm and 546.07nm. Argon, the drag gas and discharge gas, emits an intense peak at 350nm. Two emission peaks in mercury at 253.65nm and 440nm are visible with our arrangement. From the intensity of the emission lines it is possible to determine their concentration in water. [Preview Abstract] |
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LW1.00076: THERMAL PLASMAS: ARCS, JETS, SWITCHES, OTHERS |
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LW1.00077: Analyzing spotless mode of current transfer to cathodes of Cr, Gd, and Pb vapour arcs Larissa Benilova, Mikhail Benilov Diffuse mode of current transfer occurs on cathodes of vacuum arcs if the average cathode surface temperature is high enough, which can be achieved by placing the (evaporating) cathode into a thermally insulated crucible. It is shown that in the case of Cr or Pb cathodes the usual mechanism of current transfer to arc cathodes cannot sustain current densities of the order of $10^{5}-10^{6} \rm{A}\rm{m}^{-2}$ observed in the experiment, the reason being that the electrical power deposited into electron gas in the near-cathode space-charge sheath is too low. It is hypothesized that the electrical power is supplied to the electron gas primarily in the bulk plasma, rather than in the sheath, and a high level of electron energy at the sheath edge is sustained by electron heat conduction from the bulk plasma. Estimates of the current of ions diffusing to the sheath edge from the quasi-neutral plasma gave values comparable to the experimental current density, which supports the above hypothesis. On the contrary, the spotless attachment of vacuum arcs to Gd cathodes may be interpreted as a manifestation of the usual arc cathode mechanism. Results given for Gd cathodes by a model of near-cathode layers in vacuum arcs conform to available experimental information. [Preview Abstract] |
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LW1.00078: Synthesis of Amorphous Alloy Nanoparticles by Thermal Plasma Jet in a Quenching Tube Sooseok Choi, Dong-Wha Park Recently, amorphous alloy nanoparticles have received a great attention in various applications such as catalysts, compact and highly efficient transformers, electrode material for Li-ion batteries, etc. Several methods such as microwave heating, laser ablation, and sonification have been studied to synthesize amorphous metal nanoparticles. In the present work, a high velocity thermal plasma jet generated by an arc plasma torch was used to produce iron alloy nanoparticles from an amorphous raw material which was a spherical shaped powder with the mean size of 25 $\mu $m. In order to synthesize amorphous alloy nanoparticles, a quenching tube where cooling gas was injected in different axial positions. Alloy nanoparticles were produced in a relatively high input power of higher than 10 kW in a fixed powder feeding at 300 mg/min. The crystallinity of synthesized nanoparticles was decreased with increasing the quenching gas flow rate. The amorphous alloy nanoparticles were found when the quenching gas injection position was 200 mm away from the exit of the plasma torch with the highest quenching gas flow rate of 20 L/min. In the numerical analysis, the highest quenching rate was also expected at the same condition. [Preview Abstract] |
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LW1.00079: Multi-electrodes Atmospheric Pressure Plasma Jet Aiming Bio-applications Jeon G. Han, B.B. Sahu, K.S. Shin, J.S. Lee, M. Hori For the recent advancement in the field of plasma medicine, there is growing demand for the atmospheric-pressure plasma (APP) jet sources with desired plasma characteristics. In this study, a stable non-thermal low-voltage APP jet device was designed and developed for optical and electrical characterizations. The jet was operated at very low frequency in the range 10-40 KHz, which enabled the generation of low power ($\sim$ 7W) plasma with a plasma column diameter of about 5 mm. The jet has a visible radial diameter of approximately 10 mm. Optical emission spectroscopy was used as a diagnostic tool to investigate the generation of plasmas and radical species. Discharge parameters are also measured to evaluate the different operating conditions. The gas temperature measured at the substrate location varies from 300 to 315K for different gases where the electrical input power ranged from 1 to 7W. The highly reactive species like OH, O, N2, N2$+$ and along with the trace of NO are characterized with respect to the different gas flow rate of Ar/He/O2/N2, applied voltages, duty cycles and frequencies to evaluate the capability of the APP jet for future bio-applications. [Preview Abstract] |
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LW1.00080: Synthesis of Lithium Oxide Composite Nanoparticles with Spinel Structure by Induction Thermal Plasma Takuya Kageyama, Hirotaka Sone, Manabu Tanaka, Daisuke Okamoto, Takayuki Watanabe Lithium oxide composite nanoparticles were successfully synthesized by induction thermal plasma. Powder mixtures of Li$_{2}$CO$_{3}$ and MnO$_{2}$ were injected into the induction thermal plasma at 20 kW-4MHz operated in different O$_{2\, }$gas flow rates. The injected precursors were evaporated immediately in the high temperature region of the plasma and nanoparticles were produced through the quenching process. The particles were characterized by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The obtained results indicated that the nanoparticles of LiMn$_{2}$O$_{4}$ and LiMnO$_{2}$ were selectively synthesized by controlling partial pressure of O$_{2}$ in thermal plasma. Then formation mechanism of Li-based oxide nanoparticles was investigated on the basis of homogenous nucleation rate and thermodynamic consideration. In higher partial pressure of O$_{2}$, MnO nucleates and Li oxide condense on the nuclei with relatively high condensation rate, resulting in single-phase LiMn$_{2}$O$_{4}$ formation. On the other hand, in lower partial pressure of O$_{2,\, }$LiMnO$_{2}$ was obtained due to the lower condensation rate of Li oxide. [Preview Abstract] |
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LW1.00081: Effect of Lightning Impulse Discharge on PVC Thin Film Norimitsu Takamura, Takao Matsumoto, Hazuki Nerome, Kenji Mishima, Yasuji Izawa, Masahiro Hanai, Kiyoto Nishijima Lightning damage to blades of wind turbine generators has been increasing in parallel with the recent increase in the installation of the generators. According to a paper, it is said that a large current produced by a lightning penetrates into the blades, the air temperature and pressure inside the blades increase, which causes destruction of the blades. In order to solve this problem, preventing lightning penetration into the blades and passing lightning only on the surface of the blades are required. Therefore, we undertook a basic research for finding out the mechanism of lightning penetration into the blades. In this study, as our original research for clarifying the above mechanism, we investigated the effect of lightning impulse discharge on some polyvinyl chloride thin films. A high voltage electrode and a ground electrode were set with 1.0 m separation. Each film was set at the midpoint of the electrodes and approximately 750 kV of only one positive lightning impulse voltage was applied to the electrodes. After discharge, the hole-, deformed- and tarnished- diameters of the films, formed by discharge, were measured using a microscope. The results suggest that the thickness and/or the volume resistivity of the films are deeply tied to destruction of the films by discharge. [Preview Abstract] |
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LW1.00082: Synthesis of Core-shell Structured Amorphous Si Nanoparticles by Induction Thermal Plasmas Daisuke Okamoto, Takuya Kageyama, Manabu Tanaka, Hirotaka Sone, Takayuki Watanabe Core-shell structured amorphous Si nanoparticles were synthesized by induction thermal plasma. Crystalline Si powder with 3 $\mu $m of average diameter was injected into the induction thermal plasma at 4MHz. The Si raw materials immediately evaporate in the high temperature plasma region and nanoparticles were produced through the quenching process. Counterflow quenching gas was injected from downstream of the torch with its direction against the plasma flow. The effect of the operating parameter such as flow rate of quenching gas and input power was investigated. Collected particles were characterized by X-ray diffraction, transmission electron microscopy, electron energy-loss spectroscopy, and Raman spectroscopy. Obtained results indicate that amorphization degree of the synthesized nanoparticles is more than 90{\%} when additional quenching gas of 20 L/min is injected. The quenching rate of the prepared nanoparticles in the growth region have an important role on determining the amorphization degree. Moreover, EELS and Raman analyses showed the synthesized nanoparticles were coated by the SiO$_{\mathrm{2}}$ shell with thickness of 2-4 nm. These findings indicated that amorphous Si/SiO$_{\mathrm{2}}$ core-shell structured nanoparticles were successfully synthesized by induction thermal plasma in single step. [Preview Abstract] |
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LW1.00083: Prediction of SFL Interruption Performance from the Results of Arc Simulation during High-Current Phase Jong-Chul Lee, Won-Ho Lee, Woun-Jea Kim The design and development procedures of SF$_{6}$ gas circuit breakers are still largely based on trial and error through testing although the development costs go higher every year. The computation cannot cover the testing satisfactorily because all the real processes arc not taken into account. But the knowledge of the arc behavior and the prediction of the thermal-flow inside the interrupters by numerical simulations are more useful than those by experiments due to the difficulties to obtain physical quantities experimentally and the reduction of computational costs in recent years. In this paper, in order to get further information into the interruption process of a SF$_{6}$ self-blast interrupter, which is based on a combination of thermal expansion and the arc rotation principle, gas flow simulations with a CFD-arc modeling are performed during the whole switching process such as high-current period, pre-current zero period, and current-zero period. Through the complete work, the pressure-rise and the ramp of the pressure inside the chamber before current zero as well as the post-arc current after current zero should be a good criterion to predict the short-line fault interruption performance of interrupters. [Preview Abstract] |
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LW1.00084: Three-Dimensional Numerical Modeling of Free-Burning Arcs Using a CFD-MHD Coupled Method Jong-Chul Lee, Won-Ho Lee, Youn-Jea Kim Because a scientific understanding of the thermal behavior of arcs and their electrodes in free-burning arc systems is very important for improving industrial applications, numerous theoretical and experimental papers have been published in the last decade. However, the flow patterns inside the free-burning arc system must be of the 3-D feature, and 2-D modeling cannot help in predicting the 3-D flow and heat transfer within the system. This paper is concerned with developing a capability to model free-burning high-intensity argon arcs (self-consistent model) and enhancing the accuracy of numerical results according to three-dimensional calculations. It was found that the computed temperatures along the axis between the cathode tip and the anode surface show good agreement with two different measured data. Although the LTE model can reasonably predict the overall arc voltage for free-burning arcs, it fails to account accurately what happens at the near electrode region. An accurate solution near electrodes has to be based on non-LTE model to ensure current continuation in the low temperature region. Calculation of the energy flux towards the anode also requires the mechanisms operating in the non-LTE situation be taken into account in the model. [Preview Abstract] |
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LW1.00085: PLASMAS IN LIQUIDS |
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LW1.00086: Generation of Radio Frequency Plasmas in Pure Water within Hole in Insulating Plate Tsunehiro Maehara, Shinya Matsutomo, Shin Yamamoto, Shinobu Mukasa, Ayaka Tanaka, Ayato Kawashima Recently, various types of plasmas in water have been investigated. In some cases, it has been observed that plasmas in water are not in contact with the metal electrodes. In these systems, no metal electrodes contaminate water. Our research group has carried out experimental investigations on RF plasma enclosed in a bubble within a hole in an insulating plate. RF power was applied between two electrodes, and an insulating plate was placed between them. RF plasmas in pure water (0.2mS/m) and 1 wt{\%} NaCl solution can be generated within the hole, apart from the electrodes. When hole diameter is 3-10 mm, the plasmas can be maintained stably. From finite element method, the electric field and heat density before breakdown were estimated, and on the basis of those calculations it was shown that bubble formation is a key factor for plasma generation, that is, in both the cases, the existence of a bubble increases the electric field at the side of the bubble increases. These facts suggest plasma generation occurs at around the side of the bubble. However, solution can be treated as a conductor in 1 wt{\%} NaCl solution. On the other hand, in pure water, water behaves as an insulator. Therefore, different mechanisms lead to the plasma generation. [Preview Abstract] |
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LW1.00087: Characteristics of Solution Plasma Generated with Coaxial DBD Kentaro Nishimoto, Kenji Tanaka, Tatsuru Shirafuji, Shin-ichi Imai Recently, solution plasma processing, or plasma processing in or in contact with an aqueous solution, has attracted much attention because of its various possible applications. Although different types of plasma generation methods have been proposed, most of them do not cover a wide range of electrical conductivity of the water to be treated. Since the water subjected to the plasma treatment can have any values of electrical conductivity depending on the purposes of treatments, we must develop methods that cover a wide range of electrical conductivity of water. The conventional solution plasma has shown a strong dependence on the electrical conductivity of water, in which stable discharge is available only in the water with an electrical conductivity of 100$\pm$50 $\mu$S/cm. The coaxial-type DBD in contrast has shown intense discharge within the conductivity range of 0.5-160 $\mu$S/cm. This result indicates that the coaxial type DBD has more ``robust'' dependence on the electrical conductivity of water. Furthermore, the coaxial type DBD has shown 3-fold higher energy efficiency in indigo carmine degradation than the conventional solution plasma. [Preview Abstract] |
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LW1.00088: Mechanisms of Methylene Blue Degradation in Three-dimensionally Integrated Micro-solution Plasma Ayano Nomura, Yui Hayashi, Kenji Tanaka, Tatsuru Shirafuji, Motonobu Goto Plasma in aqueous solution has attracted much attention because they are expected to have possibilities to solve water-related environmental issues. In such application-oriented researches, degradation of methylene blue (MB) or other organic dyes has been widely used for investigating the effects of the plasma treatment on the water with organic contaminants. However, there are few reports on the detailed analysis of the products after the plasma treatment of MB aqueous solution for understanding mechanisms of the degradation processes. We have hence analyzed our degradation products using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. We have performed the MB degradation in three-dimensionally integrated micro-solution plasma, which has shown 16-fold higher performance in MB degradation than conventional solution plasma. The results of MALDI-TOF mass spectrometry have indicated the formation of sulfoxides in the first stage of the degradation. Then, the methyl groups on the sulfoxides are partially oxidized. The sulfoxides are separated to form two benzene derivatives after that. Finally, weak functional groups are removed from the benzene derivatives. [Preview Abstract] |
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LW1.00089: Time-resolved Optical Emission Spectroscopy on DBD of Ar Gas in Contact with Water Kazuhiko Obana, Kenji Tanaka, Tatsuru Shirafuji Recently, we have proposed three-dimensionally integrated micro-solution plasma (3D IMSP) to perform plasma treatment on a large amount of aqueous solution. In a 3D IMSP reactor, many microplasmas are generated in a porous dielectric material filled with a gas-liquid mixed medium. Time-resolved optical emission spectroscopy (OES) on 3D IMSP has revealed that the emission intensity of OH (A-X) shows unique and interesting behavior as a function of time. The OES data, however, are not those for one bubble but are averages for spatially distributed bubbles. To improve the performance of 3D IMSP, we should understand the details of plasma in one bubble. We have hence investigated the plasma generated in a simple reactor that is considered to have an environment equivalent to one bubble in 3D IMSP. The reactor has a configuration to drive dielectric barrier discharge (DBD) of Ar gas in contact with water, on which we have performed OES. The OES results have shown that the optical emission of OH (A-X) lasts longer than that of Ar. We discuss its possible mechanisms together with numerical simulation of the DBD and detailed analysis of the spectral profiles of the OH (A-X) emission. [Preview Abstract] |
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LW1.00090: Gold Nanoparticle Synthesis by 3D Integrated Micro-solution Plasma in a 3D Printed Artificial Porous Dielectric Material Naoya Sotoda, Kenji Tanaka, Tatsuru Shirafuji Plasma in contact with HAuCl$_4$ aqueous solution can promote the synthesis of gold nanoparticles. To scale up this process, we have developed 3D integrated micro-solution plasma (3D IMSP). It can generate a large number of argon microplasmas in contact with the aqueous solution flowing in a porous dielectric material. The porous dielectric material in our prototype 3D IMSP reactor, however, consists of non-regularly arranged random-sized pores. These pore parameters may be the parameters for controlling the size and dispersion of synthesized gold nanoparticles. We have hence fabricated a 3D IMSP reactor with an artificial porous dielectric material that has regularly arranged same-sized pores by using a 3D printer. We have applied the reactor to the gold- nanoparticle synthesis. We have confirmed the synthesis of gold nanoparticles through the observation of a plasmon resonance absorption peak at 550 nm in the HAuCl$_4$ aqueous solution treated with 3D IMSP. The size and distribution of the synthesized gold nanoparticles are under investigation. We expect that these characteristics of the gold nanoparticles can be manipulated by changing pore size and their distribution in the porous dielectric material. [Preview Abstract] |
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LW1.00091: Sterilization of {\it E. coli} Using 3D Integrated Micro-solution Plasma Junpei Yamamoto, Kenji Tanaka, Tatsuru Shirafuji, Takeshi Nakanishi, Masaya Kitamura Recently, sterilization of water using plasma has attracted much attention. In most cases, however, the plasma in water is quite smaller than the volume of water. To industrialize the sterilization of water using plasma, we must have appropriate plasma sources for the treatment of large-volume water. Previously, we have developed a novel reactor utilizing three-dimensionally integrated micro-solution plasma (3D IMSP). 3D IMSP generates a large number of microplasmas in contact with the aqueous solution flowing in a porous dielectric material. The 3D IMSP reactor has shown superior performance in methylene blue degradation than a conventional reactor that generates plasma between two stylus electrodes in the water. In this work, we have applied the novel 3D IMSP to the sterilization of \textit{E. coli}, and confirmed that we can sterilize the water of 150 mL with \textit{E. coli} of $10^6$ cells/mL within 6 min. We have also observed almost the same results when we treat the \textit{E. coli} with the water treated with the 3D IMSP. We discuss the possibility of the contribution of H$_2$O$_2$ and/or the other factors in our sterilization process. [Preview Abstract] |
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LW1.00092: Development of High-Throughput Liquid Treatment System using Slot Antenna Excited Microwave Plasma Sho Takitou, Michiko Ito, Seigou Takashima, Norio Nomura, Tominori Kitagawa, Hirotaka Toyoda Recently, much attention has been given to plasma production under liquid and its industrial applications as well as investigation of chemical reactions as a result of plasma-liquid interactions. In various kinds of plasma production techniques, we have proposed pulsed microwave excited plasma using slot antenna, where damage to the slot electrode can be minimized and plasma volume can be increased. Furthermore, we have proposed an in-line microwave plasma system where plasma is efficiently produced under reduced pressures using Venturi effect, and have demonstrated enhancement of organic decomposition efficiency. For practical use of the plasma liquid treatment, however, cost-effective and more efficient treatment system with high treatment capability is required. In this study, we propose further enhancement of the treatment speed by designing four-parallel-type liquid treatment device where four discharges for the treatment are performed using one microwave power source. Decomposition speed of newly-developed plasma system is investigated. Not only high decomposition rate but also enhanced energy efficiency is realized. [Preview Abstract] |
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LW1.00093: Organic Decomposition Performance of In-line Liquid Treatment System Using Microwave Plasma Michiko Ito, Seigo Takashima, Norio Nomura, Tominori Nomura, Hirotaka Toyoda Plasmas production in the vicinity of gas-liquid interface is expected as a new liquid treatment technique due to its high production rate of chemically reactive species (OH, O, etc.) and fast transfer of reactive species in liquid phase. So far, we have proposed a microwave plasma device using Venturi effect to treat a liquid, and have reported drastically-enhanced processing performance of organic decomposition by this plasma source. In this study, decomposition performance of various organic compounds such as phenol, methylene blue or diethylenetriamine is investigated. In the experiment, plasma is produced inside a gap between top and bottom parts of the nozzle by a pulsed 2.45 GHz microwave (peak power: \textless 1.2 W, pulse repetition frequency: 10 kHz). During the plasma treatment, solutions are continuously supplied to the nozzle at a flow speed of 10.5 $\sim$ 22.0 m/s. After the treatment, residual concentration is evaluated by high performance liquid chromatography, gas chromatography and so on. The result indicates the decomposition efficiency becomes different depending on organic matters. Origin of the efficiency difference will be discussed. [Preview Abstract] |
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LW1.00094: Simulation of Nanosecond Pulsed Discharge in Atmospheric Pressure Neon - Comparison between Metal Electrode and Liquid Electrode - Kazuki Motojima, Naoki Shirai, Satoshi Uchida, Fumiyoshi Tochikubo We carried out numerical simulation of nanosecond pulsed discharge in atmospheric pressure neon by two dimensional fluid model. The nanosecond pulsed discharge is generated using two types of electrode configuration; metal needle to metal plane electrodes and metal needle to liquid electrodes. The gap length between electrodes is 1 mm. In case of liquid cathode a liquid layer of 0.6 mm width is added. We confirmed the time evolution leading to bridging the gas gap from streamer propagation. Streamer has thick diameter. It is considered that streamer shape depends on a high ionization rate of neon, electrode shape, and higher applied voltage of nanosecond pulsed discharge than the breakdown voltage. We show the spatial profile of the electric field strength penetration in the liquid from the streamer. The Electric field in the liquid up to 100 kV/cm, which might induce the conductive current. Since the dielectric relaxation time is longer than the pulse width of the applied voltage, the liquid electrode almost behaves as dielectric. The influence of liquid conductivity on the discharge propagation was investigated from the viewpoint of time constant dominant for determining discharge properties. [Preview Abstract] |
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LW1.00095: Characteristics of Liquid Flow Induced by Atmospheric Pressure DC Glow Discharge with Liquid Electrode Fumiyoshi Tochikubo, Takuya Aoki, Naoki Shirai, Satoshi Uchida In the application of atmospheric-pressure discharges in contact with liquid, primary reactions are initiated between radicals and liquid molecules at plasma-liquid interface. Since the diffusion in the liquid is very slow, some convective flow is necessary to exchange the chemicals at the plasma-liquid interface for the efficient reactions. In our previous work, we found the appearance of specific downward flow in the liquid just below the dc glow discharge in contact with liquid. This downflow will be effective for exchanging the chemicals at plasma-liquid interface. In this work, we investigated the characteristics of liquid flow induced by atmospheric-pressure dc glow discharge with liquid electrode in detail; the influence of voltage polarity, current amplitude, liquid conductivity, the electrode arrangement, and so on. The spatiotemporal development of liquid flow was visualized by schlieren method, and the temperature distribution was measured using temperature-sensitive liquid crystal particles dispersed in the liquid. The liquid-flow characteristics was reproduced by a fluid simulation considering a downward driving force at liquid surface from plasma. The candidate of the driving force will be the momentum transfer of charged species at the liquid surface. [Preview Abstract] |
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LW1.00096: Shadowgraph Imaging and Numerical Simulation of Cavitation Bubbles Formed in Pulsed Laser Ablation Plasmas in the Vicinity of the Critical Point of CO$_{2}$ Hitoshi Muneoka, Shohei Himeno, Keiichiro Urabe, Sven Stauss, Motoyoshi Baba, Tohru Suemoto, Kazuo Terashima The characteristic behavior of cavitation bubbles formed in pulsed laser ablation plasmas in supercritical CO$_{2}$ were investigated by shadowgraph imaging and numerical simulations. The time evolution of the cavitation bubbles could be divided into three phases near the critical point: Expansion, Double layer formation, and Contraction. The distribution of the refractive index was estimated from the variation of the direction of the refracted light in the shockwave in the expansion phase. It was suggested that the cause of the reduction of the transmitted light in the outer shell in the double-layer phase was not due to refraction, and the contributions of nanoparticles and clusters generated in supercritical fluids were implied. The characteristics in time evolution of the bubble size in the contraction phase, in particular almost constant position of the interface in a relatively long time, was proposed to be due to zero surface tension by numerical simulations. The results suggest that the properties and fluid structure peculiar to SCF affect the structure of cavitation bubbles. [Preview Abstract] |
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LW1.00097: Attempt to control chemical reactions in liquid induced by atmospheric-pressure DC glow discharge Aihito Nito, Naoki Shirai, Satoshi Uchida, Fumiyoshi Tochikubo Nonthermal atmospheric-pressure plasmas in contact with liquid are widely studied aiming variety of plasma applications. DC glow discharge with liquid electrode is an easy method to obtain simple and stable plasma-liquid interface. When we focus attention on liquid-phase reaction, the discharge system is considered as electrolysis with plasma electrode. The plasma electrode will supply electrons and positive ions to the liquid surface in a different way from the conventional metal electrode. We tried to control the liquid phase reaction in plasma-assisted electrolysis by using the pH buffer solution to fix the pH, and by using the ion exchange membrane. The advantage of ion exchange membrane is not only the control of ion migration but the use of different solutions at anode side and cathode side. The controllability of plasma-assisted electrolysis in this work was evaluated from the temporal change of chemical species in liquid such as NO2- and NO3-, and from the metal nanoparticles generation. [Preview Abstract] |
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LW1.00098: Pulsed Picosecond and Nanosecond Discharge Development in Liquids with Various Dielectric Permittivity Constants Andrey Starikovskiy, Michael Shneider The dynamics of pulsed picosecond and nanosecond discharge development in liquid water, ethanol and hexane were investigated experimentally. Three possible mechanisms for the propagation of discharge in liquids play a different role depending on the pulse duration. The first case takes place when a ``long'' (microsecond) electric pulse applied in a non-conducting fluid: as a result of electrostatic repulsion, the formation of low density channels occurs. Consequently, the discharge propagates through the low-density regions. In the second case, under an ``intermediate'' (nanosecond) electric pulse conditions, the electrostatic forces support the expansion of nanoscale voids behind the front of the ionization wave; in the wave front the extreme electric field provides a strong negative pressure in the dielectric fluid due to the presence of electrostriction forces, forming the initial micro-voids in the continuous medium. Finally, in the third case, when a ``short'' (picosecond) electric pulse is utilized, the regions of reduced density cannot form because of the extremely short duration of the applied electric pulse. Ionization in the liquid phase occurs as a result of direct electron impact without undergoing a phase transition, occurring due to the acceleration of electrons by an external electric field comparable to the intra-molecular fields. The discharge propagates with a velocity comparable to the local speed of light. [Preview Abstract] |
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LW1.00099: NEGATIVE ION AND DUST PARTICLE CONTAINING PLASMAS |
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LW1.00100: Nonthermal and positron effects on the dust acoustic surface wave in a semi-bounded multi-component Lorentzian dusty plasma Myoung-Jae Lee, Young-Dae Jung Nonthermal and positron effects on the dust acoustic surface waves propagating at the interface between a multi-component Lorentzian dusty plasma and a vacuum are investigated. The dispersion relation is kinetically derived by employing the specular reflection boundary condition and the dielectric permittivity for dusty plasma containing positrons. We found that there exist two modes of the dust acoustic surface wave; high- and low-frequency modes. We observe that both H- and L-modes are enhanced by the increase of the pair annihilation rate. However, the effects of positron density are duplex depending on the ratio of annihilated positrons. The effects of nonthermal plasmas are also investigated on the H- and L-modes of dust acoustic surface waves. We found that the nonthermal plasmas suppress the frequencies both H- and L-modes. [Preview Abstract] |
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LW1.00101: Deposition rate and etching rate due to neutral radicals and dust particles measured using QCMs together with a dust eliminating filter Ryu Katayama, Kazunori Koga, Daisuke Yamashita, Kunihiro Kamataki, Hyunwoong Seo, Naho Itagaki, Masaharu Shiratani, Naoko Ashikawa, Masayuki Tokitani, Suguru Masuzaki, Kiyohiko Nishimura, Akio Sagara We have developed an in-situ method for measuring deposition rate of radicals and dust particles using quartz crystal microbalances (QCMs) together with a dust eliminating filter. The QCMs have three channels of quartz crystals. Channel 1 was used to measure total deposition rate due to radicals and dust particles. Channel 2 was covered with a dust eliminating filter. Channel 3 was covered with a stainless-steel plate. Moreover, all QCMs are covered with a grounded stainless steel mesh for suppressing influx of charged particles. The measurements were conducted in the Large Helical Device in the National Institute for Fusion Science, Japan. Although the deposition measurements during the discharges were difficult, we obtained deposition rate and etching rate by comparing the data before and after each discharge. The frequency difference for channel 1 changes from 0.1 Hz (etching) to -0.5 Hz (deposition), while those for channels 2 and 3 are within a range of $\pm$0.1 Hz and $\pm$0.05 Hz, respectively. The QCM method gives information on deposition rate and etching rate due to neutral radicals and dust particles. [Preview Abstract] |
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LW1.00102: Dusty Plasma Physics Facility for the International Space Station John Goree, Inseob Hahn The Dusty Plasma Physics Facility (DPPF) is an instrument planned for the International Space Station (ISS). If approved by NASA, JPL will build and operate the facility, and NASA will issue calls for proposals allowing investigators outside JPL to carry out research, public education, and outreach. Microgravity conditions on the ISS will be useful for eliminating two unwanted effects of gravity: sedimentation of dust particles to the bottom of a plasma chamber, and masking weak forces such as the ion drag force that act on dust particles. The DPPF facility is expected to support multiple scientific users. It will have a modular design, with a scientific locker, or insert, that can be exchanged without removing the entire facility. The first insert will use a parallel-plate radio-frequency discharge, polymer microspheres, and high-speed video cameras. This first insert will be designed for fundamental physics experiments. Possible future inserts could be designed for other purposes, such as engineering applications, and experimental simulations of astrophysical or geophysical conditions. The design of the facility will allow remote operation from ground-based laboratories, using telescience. [Preview Abstract] |
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LW1.00103: Perpendicular diffusion of a dilute beam of charged particles in the PK-4 dusty plasma Bin Liu, John Goree We study the random walk of a dilute beam of projectile dust particles that drift through a target dusty plasma. This random walk is a diffusion that occurs mainly due to Coulomb collisions with target particles that have a different size. In the direction parallel to the drift, projectiles exhibit mobility-limited motion with a constant average velocity. We use a 3D molecular dynamics (MD) simulation of the dust particle motion to determine the diffusion and mobility coefficients for the dilute beam. The dust particles are assumed to interact with a shielded Coulomb repulsion. They also experience gas drag. The beam particles are driven by a prescribed net force that is not applied to the target particles; in the experiments this net force is due to an imbalance of the electric and ion drag forces. This simulation is motivated by microgravity experiments, with the expectation that the scattering of projectiles studied here will be observed in upcoming PK-4 experiments on the International Space Station. \\[4pt] [1] Bin Liu and J. Goree, Physics of Plasmas, 21, 063704 (2014). [Preview Abstract] |
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LW1.00104: Laser trapped single fine particle as a probe of plasma parameters Daisuke Yamashita, Masahiro Soejima, Teppei Ito, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani Here we report evaluation of electron density and temperature using optically trapped single fine particle. Experiments were carried out with a radio frequency low pressure plasma reactor, where we set two quartz windows as top and bottom flanges to irradiate an infrared laser light of 1064 nm wavelength from the bottom side [1]. Ar plasmas were generated between a powered ring-electrode set at the bottom of the reactor and a grounded mesh placed at the center of the reactor at 100 Pa by applying 13.56MHz voltage. The particles injected into the plasmas were monodisperse methyl methacrylate-polymer spheres of 10 $\mu$m in diameter. A negatively charged particle, which is suspended plasma sheath boundary, was trapped at the focal point of the irradiated laser light due to the transfer of momentum from the scattering of incident photons. At the beginning of the trapping, particle of 10 $\mu$m in size was trapped above 505 $\mu$m from the bottom window. After 230 min, the size and position were 9.56 $\mu$m and 520 $\mu$m, respectively. From the results, the electron density and temperature are deduced to be 1.7x10$^{9}$ cm$^{-3}$ and 1.9 eV.\\[4pt] [1] T. Ito, et al., J. Phys.: Conf. Ser. 518(2014)012014. [Preview Abstract] |
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LW1.00105: Effect of energetic electrons for dust charging in a large rectangular RF helium plasma SoonGook Cho, Taehyeop Lho, Kyu-Sun Chung A large rectangular RF plasma device (44 x 50 x 120 cm$^{3}$) has been developed for the study of transport and removal of dusts. Effects of dust grains and properties of background plasma are investigated by a planar electric probe in dusty plasma, which is consisted of helium plasma and tungsten dust. To check effect of the energetic electrons on the charging process, low density energetic electrons are produced by applying negative bias to a meshed tungsten grid installed between the upper power electrodes of RF antenna and the bottom ground electrodes. Density and charge of dusts are deduced by comparing pure helium plasma to that of dusty helium plasma. [Preview Abstract] |
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LW1.00106: Development of cesium-free negative hydrogen ion source by using sheet plasma Takuya Hase, Takaaki Iijima, Yuta Tanaka, Tosikio Takimoto, Akira Tonegawa, Kohnosuke Sato, Kazutaka Kawamura We demonstrated the production of hydrogen negative ions in cesium-free discharge by using the magnetized sheet plasma. Plasma crossed with a vertical gas flow system and extracting H$^{\mathrm{-}}$ beams from the sheet plasma. Under a secondary hydrogen gas entering the hydrogen plasma, the peak position of the hydrogen plasma is localized in the periphery of the sheet plasma. The maximum negative ion beam is successfully extracted using grids located in the periphery of the sheet plasma. The extraction current density is about 8 mA/cm$^{\mathrm{2}}$ at extraction voltage is 2 kV and discharge current of 30 A. The extraction negative ion current density is saturated at the extraction voltage is 2 kV for the limit of the negative ion density in the periphery region of the sheet plasma. On the other hand, the extraction current is saturated (3 mA/cm$^{\mathrm{2}})$ with increasing extraction voltage and the negative ions are not detected without the secondary gas flow (0 sccm). This curve depends on the electrons present. Therefore, it is considered that the negative ion current against the extraction current is around 60{\%} from the ratio of the extraction current and the extraction electron current. [Preview Abstract] |
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LW1.00107: OTHER PLASMA SCIENCE TOPICS |
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LW1.00108: Research on OH(A) Production Mechanism of an Atmospheric He-Water Plasma Jet Jingjing Liu, Xiao Hu Hydroxyl radicals produced by atmospheric liquid containing plasmas play important role on bacteria killing and wound healing. A He-H$_{2}$O plasma jet can produce abundant OH radicals with low gas temperature. At present, some possible reactions to produce OH(A) are concluded, however, the main mechanism to produce OH(A) and the influence of plasma working mode and water vapor concentration on OH(A) generation are still not clear. It is generally regarded that the accurate measurements of electron density and electron temperature play key role on the analysis of OH production mechanism. In this paper, the main generation and loss mechanisms of OH(A) will be found out by both experimental measurements of time-spatial distribution of OH(A) emission intensity, electron density and electron temperature and neutral gas/plasma fluid simulation at different working modes and water vapor concentrations. The influence of plasma working mode and water vapor concentration on OH(A) production and its flux arriving on the substrate is also investigated to optimize the He-H$_{2}$O plasma jet for bio-medical application. [Preview Abstract] |
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LW1.00109: The study of data collection method for the plasma properties collection and evaluation system from web Jun-Hyoung Park, Mi-Young Song Plasma databases are necessarily required to compute the plasma parameters and high reliable databases are closely related with accuracy enhancement of simulations. Therefore, a major concern of plasma properties collection and evaluation system is to create a sustainable and useful research environment for plasma data. The system has a commitment to provide not only numerical data but also bibliographic data (including DOI information). Originally, our collection data methods were done by manual data search. In some cases, it took a long time to find data. We will be find data more automatically and quickly than legacy methods by crawling or search engine such as Lucene. [Preview Abstract] |
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LW1.00110: Study of Pulsed vs. RF Plasma Properties for Surface Processing Applications Ricky Tang, Matthew Hopkins, Edward Barnat, Paul Miller The ability to manipulate the plasma parameters (density, E/N) was previously demonstrated using a double-pulsed column discharge. Experiments extending this to large-surface plasmas of interest to the plasma processing community were conducted. Differences between an audio-frequency pulsed plasma and a radio-frequency (rf) discharge, both prevalent in plasma processing applications, were studied. Optical emission spectroscopy shows higher-intensity emission in the UV/visible range for the pulsed plasma comparing to the rf plasma at comparable powers. Data suggest that the electron energy is higher for the pulsed plasma leading to higher ionization, resulting in increased ion density and ion flux. Diode laser absorption measurements of the concentration of the 1S5 metastable and 1S4 resonance states of argon (correlated with the plasma E/N) provide comparisons between the excitation/ionization states of the two plasmas. Preliminary modeling efforts suggest that the low-frequency polarity switch causes a much more abrupt potential variation to support interesting transport phenomena, generating a ``wave'' of higher temperature electrons leading to more ionization, as well as ``sheath capture'' of a higher density bolus of ions that are then accelerated during polarity switch. [Preview Abstract] |
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LW1.00111: PLASMA ION IMPLANTATION |
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LW1.00112: Low-energy Plasma Ion Implantation Noriyuki Sakudo, Noriaki Ikenaga, Kei Matsui We formerly showed that deposited film of NiTi can be crystallized at very low substrate temperature without any post-annealing treatment by using simultaneous ion irradiation with sputter deposition. Since the ion energy for optimum crystallization was around 80 eV which was very low compared with usual plasma ion implantation, the ion acceleration voltage was determined by the potential difference between the pulse bias voltage which was negative and the plasma potential which was positive with respect to the grounded chamber. In this study we find that the plasma potential itself changes as functions of the bias voltage as well as the configuration factor, i.e., the area ratio of the bias electrode surface to the chamber wall surface. In order to get the exact ion energy we obtain a new formula for plasma potential by deducing from the equation for continuity of charged-particle currents in plasma. Resultantly, it is shown that the plasma potential differs from that obtained by the conventional simple plasma model, especially when the electron temperature and/or the configuration factor become higher. In some cases the bias voltage might be positive in order to keep the ion energy as low as around 80 eV. [Preview Abstract] |
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LW1.00113: Ion extraction optics with tunable ion angular distribution of ribbon beams Costel Biloiu, Daniel Distaso, Christopher Campbell, Vikram Singh, Anthony Renau The characteristics of the ion angular distribution (IAD) of an extracted ion beam are determined by the shape, location, and orientation of the plasma meniscus. We describe an electrostatic lens that allows modification of plasma meniscus topology and as a result in situ control of the IAD of extracted ribbon ion beams, i.e., control of ion mean angle and angular spread. The ion extraction optics supposes the use of an electrode immersed in the plasma which is located adjacent to the extraction slit. By electrically biasing the electrode relative to the plasma, the meniscus topology and its orientation relative to the wafer plane can be controlled. Thus, 300 mm wide ribbon ion beams with characteristic mean angle spanning from $0^{\circ}$ to $50^{\circ }$ and angular spread as low as $4^{\circ}$ can be obtained. Ion angular distribution can be tuned in terms of mean angle and angular spread for different ion beam energies and beam currents. In addition, being made of conductive material, the extraction optics is insensitive to the possible conductive deposits resulting from byproducts of ion beam bombardment of the wafer surface. [Preview Abstract] |
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LW1.00114: Adjustable, High Voltage Pulse Generator with Isolated Output for Plasma Processing Timothy Ziemba, Kenneth E. Miller, James Prager, Ilia Slobodov Eagle Harbor Technologies (EHT), Inc. has developed a high voltage pulse generator with isolated output for etch, sputtering, and ion implantation applications within the materials science and semiconductor processing communities. The output parameters are independently user adjustable: output voltage (0 -- 2.5 kV), pulse repetition frequency (0 -- 100 kHz), and duty cycle (0 -- 100{\%}). The pulser can drive loads down to 200 $\Omega $. Higher voltage pulsers have also been tested. The isolated output allows the pulse generator to be connected to loads that need to be biased. These pulser generators take advantage modern silicon carbide (SiC) MOSFETs. These new solid-state switches decrease the switching and conduction losses while allowing for higher switching frequency capabilities. This pulse generator has applications for RF plasma heating; inductive and arc plasma sources; magnetron driving; and generation of arbitrary pulses at high voltage, high current, and high pulse repetition frequency. [Preview Abstract] |
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LW1.00115: GREEN PLASMA TECHNOLOGIES: ENVIRONMENTAL AND ENERGY APPLICATIONS |
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LW1.00116: Photocatalytic characterization of oxygen vacancy TiO$_{2}$ prepared with Ar/H$_{2}$ plasma surface treatment Takuma Nakano, Sumio Kogoshi, Noboru Katayama It has been observed that oxygen vacancy TiO2 (TiO$_{2-x}$) prepared with Ar/H2 plasma surface treatment have an optimal process condition for visible light photocatalytic activity. However it may depend on the plasma process system. Therefore, it is desirable to describe the optimal condition with a more general term, for example the x value of TiO$_{2-x}$. In addition the reason why the optimal condition exists is unclear. In this study, we carried out the measurement to find out the dependence of visible light photocatalytic activity on the x value and ab initio calculation of density of states (DOS) of TiO$_{2-x}$. The dependence of visible light photocatalytic activity of TiO$_{2-x}$ on the x value has been estimated experimentally. When the x value was 0.069, the visible light photocatalytic activity was optimal. The results of the calculation have suggested a new oxygen vacancy state would emerge at a nearly center between the valence band and the conduction band for larger x values. This result implies that the recombination rate between electrons and holes would increase, resulting in less photocatalytic activity for the larger x value. [Preview Abstract] |
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LW1.00117: Optical Engines, Organic Spintronics \& Ice-Cube/Astranomcs Notions Fatahillah Hidajatullah-Maksoed, Fauzan Faizal-Imaduddin Refers to ``Optical engines for light energy detection,'' PhysicsToday,June 2012, h 60 denotes NewPortCorp's OptoFlash is a miniature multichannel spectrometer engine that detects lght energy at multiple wavelengths. According to NewPort, the demultiplexing optical engine is easy to customize. Involves the Computational Fluid Dynamics/ContractForDifferences, there were sought for ``LaserDopplerVelocimetry/LDV, we intended to comprises the lVDT include in Sensor technology as well as to PVDF/polyvynilidine fluoride who comprises giant flexoelectric in alpha-phase-Xiaoning Jiang,et.al:``Flexoelectric Nanogenerator:Materials, structures \& devices,'' 2013 paved with good intentions, the ``jellium model''[Overhauser, 1963a ] maybe can be interrelated to reflex action \& primary process used by Id to avoids pain in painstakingly to wieghs spin relaxation \& dephasing process that guides ``EQILIBRATION.'' Also offered the spintronics using PID-controller, from Microbisl Cells to ``The Motor Response inPlasma Heating.'' Further, the Aug 1985 FAA Certification for IAI 1125 ASTRA Jet Corp inherently existed between Julian C. Blecker's dissertation to ``realistic mathematics'' from Prof. R.K. Sembiring/MA-ITB. [Preview Abstract] |
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LW1.00118: Reforming of biogas to synthesis gas by a rotating arc plasma at atmospheric pressure Woo-Jae Chung, Hyun-Woo Park, Jing-Lin Liu, Dong-Wha Park In order to produce synthesis gas, reforming of biogas composed with 60 percent for CH4 and 40 percent for CO2 was performed by a novel rotating arc plasma process. The effect of O2/CH4 ratio on the conversion, syngas composition and energy cost was investigated to evaluate the performance of proposed system compared with conventional gliding arc plasma process. When the O2/CH4 ratio was increased from 0.4 to 0.9, the conversions of CH4 and O2 increased up to 97.5 percent and 98.8 percent, respectively, while CO2 conversion was almost constant to be 38.6 percent. This is due to more enhance the partial oxidation of CH4 to CO and H2 than that of dry reforming by increasing the O2/CH4 ratio. In this work, energy cost of 32 kJ/mol was achieved with high syngas composition of 71 percent using pure O2 as oxidant reactant. These are lower than those of different arc plasma processes (energy cost of 122 - 1870 kJ/mol) such as spark, spark-shade and gliding arc plasma. Because, this rotating arc plasma can remain in a long arc length and a large volume of plasma with constant arc length mode. [Preview Abstract] |
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LW1.00119: Conversion of CO$_{2}$ to CH$_{4}$ by a coaxial hydrogen plasma shower method Satoru Iizuka, Keisuke Arita Conversion of CO$_{2}$ to CH$_{4}$ was investigated by using a coaxial hydrogen plasma shower method. Hydrogen radicals produced by hydrogen plasma in an inner tube were ejected through a narrow channel between a core rod electrode and the inner tube toward downstream reaction region, where carbon dioxide was supplied from an outer tube. Conversion rate of CO$_{2}$ to CH$_{4}$ was investigated by changing the discharge parameters such as applied voltage, gas flow rate, and so on. Carbon dioxide was successively reduced by hydrogen radicals. Maximum conversion rate of about 50{\%} was established. This system provided very efficient conversion of CO$_{2}$ to CH$_{4}$. [Preview Abstract] |
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LW1.00120: Influence of Sodium Carbonate on Decomposition of Formic Acid by Discharge inside Bubble in Water Masashi Iwabuchi, Katsuyuki Takahashi, Koichi Takaki, Naoya Satta An influence of sodium carbonate on decomposition of formic acid by discharge inside bubble in water was investigated. Oxygen or argon gases were injected into the water through a vertically positioned glass tube, in which the high-voltage wire electrode was placed to generate plasmas at low applied voltage. The concentration of formic acid was determined by ion chromatography. In the case of addition of sodium carbonate, the pH value increased with decomposition of the formic acid. In the case of oxygen injection, the increase of pH value contributed to improve an efficiency of the formic acid decomposition because the reaction rate of ozone and formic acid increased with increasing pH value. In the case of argon injection, the decomposition rate was not affected by the pH value owing to the high rate constants for loss of hydroxyl radicals. [Preview Abstract] |
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LW1.00121: A Compact Plasma Flow-Bubbler for Decomposition of Organic compounds and Sterilization Hiroyuki Yoshiki, Fukuto Ishikawa, Yu Igarashi, Tetuya Sugawara Recently, Plasma production in and in contact with liquid has attracted much attention because of their applications to degradation of organic compounds, sterilization, water purification. UV, electron, ion and radical flows originated from a plasma and also shock wave induce physical and chemical reaction in a liquid, for example oxidation-reduction, electrolysis and reactive species production in a water. In particular, various reactive oxygen/nitrogen species generated at the plasma-liquid interface play an important role in oxidation and degradation of organic pollutants and bacteria. We have proposed the mild water treatment by ejecting the atmospheric-pressure $\mu$plasma (AP$\mu$P) flow into a water using a microbubble aerator or a porous ceramics bubbler. In this study, a compact plasma flow-bubbler made up of a $\mu$plasma source and a porous ceramics has been developed for the applications of water purification and sterilization. AP$\mu$P is generated between a thin metal pipe electrode and a GND plate by a pulsed high voltage, so that the O$_{2}$ $\mu$plasma can be obtained without adding He and Ar gases. Plasma flow is ejected into the water through a porous ceramics. Decolorization of an indigo carmine solution strongly depended on O$_{2}$ flow rate. Chemical probe method using terephthalic acid revealed that OH radicals are produced by the O$_{2}$ plasma gas bubbling. The inactivation for \textit{E. coli}, \textit{Bacillus subtilis} was attained by the O$_{2}$ plasma gas bubbling. [Preview Abstract] |
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LW1.00122: CH$_{4}$-CO$_{2}$ reforming in surface DBD reactor with ZnO-Cu and NiO catalysts Claudia Lazzaroni, Abdelkader Rahmani, Mehrdad Nikravech Dry reforming of methane (CH$_4$) is carried out in an atmospheric pressure Dielectric Barrier Discharge (DBD) reactor. The two 3 mm thickness aluminum electrodes are separated by a 3 mm thickness dielectric sheet made of quartz. The electrodes present 3 branches and the space between two adjacent branches is filled with beads of catalyst which are 2 mm diameter alumina beads coated with ZnO-Cu or NiO. The coating is performed in two different ways: (i) by impregnation and (ii) by fluidized spray plasma. A 30 kHz and several kV AC voltage is applied to the electrodes. The feedstock gas is a mixture of argon, carbon dioxide (CO$_{2})$ and methane with individual fluxes varying from 20 to 80 mL/min. At the reactor outlet, the gas goes through a condenser at 4$^{\circ}$C to condense liquid products. The reforming reaction products are identified by liquid and gas phase chromatography. The effect of the applied power and the catalyst nature on the product distribution is studied. Whatever the catalyst, the conversion rate of CH$_{4}$ and CO$_{2}$ increases with the applied power while the selectivity of gas products is almost independent of the power. The condensed liquids collected under our experimental conditions, such as ethanol or acetic acid, represent more than 10{\%} of the products. [Preview Abstract] |
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LW1.00123: Generation of pulsed discharge plasma in water with fine bubbles Yui Hayashi, Noriharu Takada, Hideki Kanda, Motonobu Goto Recently, some researchers have proposed electric discharge methods with bubbles in water because the discharge plasma inside bubble was easy to be generated compared to that in water. Almost all of these methods introduced bubbles in the order of millimeter size from a nozzle placed in water. In these methods, bubbles rose one after another owing to high rising speed of millibubble, leading to inefficient gas consumption. We proposed fine bubbles introduction at the discharge area in water. A fine bubble is determined a bubble with less than 100 $\mu$m in a diameter. Fine bubbles exhibit extremely slow rising speed. Fine bubbles decrease in size during bubble rising and subsequently collapse in water with OH radical generation. Therefore, combining the discharge plasma with fine bubbles is expected to generate more active species with small amount of gas consumption. In this work, fine bubbles were introduced in water and pulsed discharge plasma was generated between two cylindrical electrodes which placed in water. We examined effects of fine bubbles on electric discharge in water when argon or oxygen gas was utilized as feed gas. Fine bubbles enhanced optical emission of hydrogen and oxygen atoms from H$_{2}$O molecules, but that of feed gas was not observed. The formation mechanism of H$_{2}$O$_{2}$ by electric discharge was supposed to be different from that with no bubbling. Dissolved oxygen in water played a role in H$_{2}$O$_{2}$ formation by the discharge with fine bubbles. [Preview Abstract] |
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LW1.00124: Enhancement of burning velocity by dissociated oxygen atoms Haruaki Akashi, Tomokazu Yoshinaga, Koichi Sasaki Green technology, such as preventing global warming, has been developed for years. Researches on plasma assisted combustion is one of the technologies and have been done for investigating more efficient combustion, more efficient use of fossil fuel with plasmas or applying electric fields. In the ignition time delay analyses with the dissociated oxygen atoms which is generated by non-equilibrium plasma had significant effect on the ignition time. In this paper, dissociated oxygen could effect on burning velocity or not has been examined using CHEMKIN. As a result, no effect can be seen with dissociation degree of lower than 10$^{-3}$. But there is an effect on the enhancement of burning velocity with higher degree of 10$^{-3}$. At the dissociation degree of 5x10$^{-2}$, the burning velocity is enhanced at a factor of 1.24. And it is found that the distributions of each species in front of preheat zone are completely different. The combustion process is proceeded several steps in advance, and generation of H$_{2}$O, CO and CO$_{2}$ can be seen before combustion in higher dissociation case. [Preview Abstract] |
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LW1.00125: Evaluation of Applied Magnetic Field on Reduction Efficiency of Alumina Powder Sato Yusuke, Ryo Myoen, Makoto Matsui, Kimiya Komurasaki, Yoshihiro Arakawa Alumina reduction method using laser sustained plasma (LSP) is proposed for energy storage system using aluminum. In our previous study, the averaged reduction efficiency in the plasma was estimated as five percent. Aluminum has property which is easily oxidized. Therefore, active separation of oxygen and aluminum is important for enhancement of collection efficiency. In this research, Al ion is separate from oxygen by applying magnetic field. [Preview Abstract] |
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LW1.00126: Production of composite Si nanoparticles by plasma spraying PVD and CH$_{4}$ annealing for negative electrodes of lithium ion batteries Ryoshi Ohta, Yutaro Ohta, Toru Tashiro, Makoto Kambara Si is a promising candidate as anode of next generation high density Li ion batteries. This material, however, needs to be nanostructured, nanoparticles and C coating of active material, to cope with huge volume change and associated rapid capacity decay. Si nanoparticles with 20--40 nm have been successfully produced by plasma spraying PVD and also Si-C core-shell composite particles by adding CH$_{4}$ during processing. The battery performance has been improved with these nanopowders as anode, especially with the C coated Si particles. However, SiC that is inactive in battery reaction forms inevitably at high temperature during plasma spraying PVD and reduces the capacity density. In this work, therefore, post CH$_{4}$ annealing was attempted to form Si-C nanocomposite particles while suppressing formation of SiC. The primary Si nanoparticles were unchanged in size after annealing and were coated with the finer carbonous particles that formed after CH$_{4}$ infiltration through pores between nanoparticles. The batteries using annealed powders with C/Si molar ratio of 0.3 have shown two-fold capacity retention increase after 50 cycles with no capacity reduction associated with SiC formation as compared to the powders without C. [Preview Abstract] |
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LW1.00127: Dielectric Barrier Discharge Methane Conversion Chong Liu, Alexander Fridman, Alexander Rabinovich, Danil Dobrynin With the large amount of nature gas discovery every year, there is an increasing interest on modification of methane. The fact that methane is gaseous makes it less economic and efficient than liquid fuel. Here we propose a new way of converting methane from gas phase to liquid phase. Dielectric barrier discharge is used to treat methane and nitrogen mixture bubbles inside of liquid fuel. Nitrogen is here to help activate methane into an excited state, then it is possible for the excited molecules to react with other liquid hydrocarbon. Gaseous methane is converted in to liquid phase when excited methane replace a hydrogen and add onto the carbon chain. In this study some preliminary experiments is done to verify this hypothesis. There is equivalent weight increases with methane and nitrogen mixture discharging in diesel when compare to only nitrogen discharging in diesel. The same experiment have also been done with gas mixture discharged in 1-methylnaphthalene. And FTIR analysis of the after treatment hydrocarbon liquid all indicates that there is an increasing in C-H bond concentration and a decreasing in phenyl ring structure. [Preview Abstract] |
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LW1.00128: PLASMA PROCESSING FOR PHOTOVOLTAIC APPLICATIONS |
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LW1.00129: Effects of electrode structure on characteristics of multi-hollow discharges Yoshihiro Torigoe, Kimitaka Keya, Susumu Toko, Hyunwoong Seo, Haho Itagaki, Kazunori Koga, Masaharu Shiratani Silane plasmas are widely employed for hydrogenated amorphous silicon (a-Si:H) film deposition. Amorphous silicon nanoparticles below 10 nm in size (clusters) are formed in silane plasmas and some of them are incorporated into a-Si:H films, leading to the light induced degradation which is the most important issue for a-Si:H solar cells. To suppress cluster incorporation, a multi-hollow discharge plasma CVD method has been developed and succeeded in depositing highly stable a-Si:H films. For further improvement of the film qualities, we have employed a thicker grounded electrode to suppress plasma expansion toward the deposition region. From optical images of the discharge plasmas, the expansion was significantly suppressed using 10 mm thick grounded electrode. For the 10 mm thick electrode, optical emission intensity ratio of Si* (288 nm) and SiH* (414 nm) I$_{\mathrm{Si\ast }}$/I$_{\mathrm{SiH\ast }}$, which shows a ratio of cluster generation ratio and radical ones, was 20 {\%} of that for 1mm thick electrode. These results suggest that the generation of clusters was also suppressed using the 10 mm thick grounded electrode. [Preview Abstract] |
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LW1.00130: Investigation the cause of plasma treatment for low temperature annealed dye-sensitized solar cells Shungo Zen, Yuta Komatsu, Ryo Ono Dye-sensitized solar cells (DSSCs) require annealing of TiO$_{2}$ photoelectrodes at 450 C to 550 C. However, such high-temperature annealing is unfavorable because it limits the use of materials that cannot withstand high temperatures, such as plastic substrates. In our previous paper, a low temperature annealing technique of TiO$_{2}$ photoelectrodes using ultraviolet light and dielectric barrier discharge treatments was proposed to reduce the annealing temperature from 450 C to 150 C for a TiO$_{2}$ paste containing an organic binder. Here, we investigated the cause of plasma treatment via the Nyquist diagram (Cole-Cole plot) of DSSCs. The Nyquist diagram was masured with a frequency response analyzer (NF Corporation, FRA5022) under 100 mW/cm$^{2}$ illumination of a calibrated xenon lamp (Hamamatsu L2274, 150W). The lifetime of the electrons, the effective electron diffusion coefficient, and the electron diffusion length of TiO$_{2}$ photoelectrodes were determined by analyzing the Nyquist diagrams. As a result of analyzing the Nyquist diagrams, it was shown that plasma treatment can reduce the electron transport resistance and promote the necking of Hot UV annealed TiO$_{2}$ nanoparticles. [Preview Abstract] |
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LW1.00131: Ratio of Cu, Zn, Sn and S densities in magnetron sputtering plasmas employing a stoichiometric Cu$_2$ZnSnS$_4$ target Nayan Nafarizal, Koichi Sasaki Recently, Cu$_2$ZnSnS$_4$ (CZTS) has drawn wide attention as a highly potential material for the next-generation thin film solar cells. In order to optimize CZTS thin films for solar cells, it is essential to understand their deposition mechanism. Especially since it consists of four elements, it is difficult to control the stoichiometric properties. In the present work, we measured the absolute ground-state densities of Cu, Zn, Sn, and S atoms released from a stoichiometric CZTS target in magnetron sputtering plasmas. The absolute atom densities were evaluated by ultraviolet and vacuum ultraviolet absorption spectroscopy. Magnetron sputtering plasmas were produced using a pulsed-modulated rf power supply and the temporal variations of atom densities were measured in the afterglow. The absolute Cu, Zn, Sn and S densities in the discharge phase were evaluated by the extrapolations of the temporal variations. It has been observed that the absolute Cu, Zn, Sn and S densities in the gas phase were not in agreement with the stoichiometry of the target as well as that of the deposited film. The results suggest possibilities of unconventional sputtering and deposition processes in the compound sputter deposition. [Preview Abstract] |
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LW1.00132: Raman spectroscopy of PIN hydrogenated amorphous silicon solar cells Kimitaka Keya, Yoshihiro Torigoe, Susumu Toko, Daisuke Yamashita, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani Light-induced degradation of hydrogenated amorphous silicon (a-Si:H) is a key issue for enhancing competitiveness in solar cell market. A-Si:H films with a lower density of Si-H$_{2}$ bonds shows higher stability [1]. Here we identified Si-H$_{2}$ bonds in PIN a-Si:H solar cells fabricated by plasma CVD using Raman spectroscopy. A-Si:H solar cell has a structure of B-doped $\mu $c-SiC:H (12.5 nm)/ non-doped a-Si:H (250nm)/ P-doped $\mu $c-Si:H (40 nm) on glass substrates (Asahi-VU). By irradiating HeNe laser light from N-layer, peaks correspond to Si-H$_{2}$ bonds (2100 cm$^{-1})$ and Si-H bonds (2000 cm$^{-1})$ have been identified in Raman scattering spectra. The intensity ratio of Si-H$_{2}$ and Si-H I$_{\mathrm{SiH2}}$/I$_{\mathrm{SiH}}$ is found to correlate well to light induced degradation of the cells Therefore, Raman spectroscopy is a promising method for studying origin of light-induced degradation of PIN solar cells.\\[4pt] [1] T. Nishimoto, et al., J. Non-Crystal. Solids 299-302 (2002) 1116. [Preview Abstract] |
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LW1.00133: Effects of N$_{2}$ dilution on fabrication of Ge nanoparticles by rf sputtering Shnji Hashimoto, Souta Tanami, Hyunwoong Seo, Giichiro Uchida, Daisuke Yamashita, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masharu Shiratani Multiple exciton generation (MEG) in QDs is expected to enhance significantly the energy conversion efficiency of solar cells. Although there are several reports on MEG characteristics from various QD materials such as PbS, CdSe, CdS ZnS, and Ag$_{2}$S, such materials have disadvantages of their toxicity and limited resources. Here we have developed quantum-dots (QDs) solar cells using Ge nanoparticles fabricated by rf sputtering method under high pressure. We fabricated Ge nanoparticles by rf sputtering at a pressure of 1.5 Torr. Since the mean free path of Ge atoms is an order of micrometer, and Ge nanoparticles are formed in gas phase. We fabricated Ge nanoparticles using Ar and N$_{2}$ to terminate surface defects by N. Ge and Ar emission intensities decrease significantly with increasing N$_{2}$ partial pressure. The electron density was measured with a plasma absorption probe. The electron density decreases with increasing N$_{2}$ partial pressure. [Preview Abstract] |
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LW1.00134: Femtosecond Laser Processing Characterization of Organic Thin Film Norio Tsuda, Yuki Makino, Jun Yamada Laser processing characterization of organic thin film solar cell is important for solar cell production technique. Femtosecond laser is able to process low thermal damage processing. Laser processed surface of organic thin film is checked and the processing characterization is investigated. [Preview Abstract] |
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LW1.00135: BIOLOGICAL APPLICATIONS OF PLASMAS |
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LW1.00136: Effects of Ambient Humidity on Plant Growth Enhancement by Atmospheric Air Plasma Irradiation to Plant Seeds Thapanut Sarinont, Takaaki Amano, Kazunori Koga, Masaharu Shiratani Humidity is an important factor for plasma-bio applications because composition of species generated by atmospheric pressure plasmas significantly depends on the humidity [1]. Here we have examined effects of humidity on the growth enhancement to study the mechanism. Experiments were carried out with a scalable DBD device [2]. 10 seeds of \textit{Raphanus sativus L}. were set for x$=$ 5 mm and y$=$ 3 mm below the electrodes. The humidity H$_{\mathrm{air}}$ was 10 - 90 {\%}Rh. The ratio of length of plants with plasma irradiation to that of control increases from 1.2 for H$_{\mathrm{air}}=$ 10 {\%}Rh to 2.5 for H$_{\mathrm{air}}=$ 50 {\%}Rh. The ratio is 2.5 for H$_{\mathrm{air}}=$ 50-90 {\%}Rh. This humidity dependence is similar to the humidity dependence of O$_{2}^{+}$-H$_{2}$O, H$_{3}$O*, NO$_{2}^{-}$-H$_{2}$O and NO$_{3}^{-}$-H$_{2}$O densities, whereas it is different from that of other species such as O$_{3}$, NO, and so on [1]. The similarity gives information on key species for the growth enhancement.\\[4pt] [1] T. Murakami, et al., Plasma Sources Sci. Technol. 22, 015003 (2013).\\[0pt] [2] S. Kitazaki, et al., Curr. Appl. Phys., 14, S149 (2014). [Preview Abstract] |
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LW1.00137: Characterization of Atmospheric Pressure Plasma Jet (APPJ) and Its Effect on Plasmid DNA Ek Adhikari, Sylwia Ptasinska A helium atmospheric pressure plasma jet (APPJ) source was constructed and then characterized by monitoring a deflected current on a high voltage electrode and a potential difference between two electrodes. The deflected current was also monitored for the APPJ source with varied electrical and fed gas composition e.g. admixtures of He and water vapor. The deflected power per cycle for gas admixtures was decreased with the increase in fraction of water vapor. In addition, this APPJ source was used to induce damage to aqueous plasmid DNA. The fraction of supercoiled, single-strand breaks and double-strand breaks in DNA were quantified by using agarose gel electrophoresis. The number of DNA strand breaks increased as a function of plasma irradiation time and decrease as a distance between APPJ and DNA sample increased. The APPJ with the gas admixture, in which the fraction of water vapor was varied, was also used to induce damage to aqueous DNA samples. The damage level decreased with the increase in a fraction of water vapor under specific experimental conditions. The change in numbers of DNA strand breaks irradiated by a pure He plasma and a plasma with a gas admixture is predicted by different physical and chemical process in the APPJ. [Preview Abstract] |
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LW1.00138: Study on the role of active radicals on plasma sterilization inside small diameter flexible polymeric tubes Hiroto Mstsuura, Takatomo Fujiyama, Yasuki Okuno, Masakazu Furuta, Shuichi Okuda, Yuichiro Takemura Recently, atmospheric pressure discharge plasma has gathered attention in various fields. Among them, plasma sterilization with many types of plasma source has studied for decades and its mechanism is still an open question. If active radicals produced in plasma has main contribution of killing bacterias, direct contact of the so-called plasma flame might not be necessary. To confirm this, sterilization inside small diameter flexible polymeric tubes is studied in present work. DBD type plasma jet is produce by flowing helium gas in a glass tube. A long polymeric tube is connected and plasma jet is introduced into it. Plasma flame length depends on helium gas flow rate, but limited to about 10 cm in our experimental condition. E.colis set at the exit plasma source is easily killed during 10 min irradiation. At the tube end ( about 20 cm away from plasma source exit ), sterilization is possible with 30 min operation. This result shows that active radical is produced with helium plasma and mist contained in sample, and it can be transferred more than 20 cm during it life time. More plasma diagnostic data will also be shown at the conference. [Preview Abstract] |
(Author Not Attending)
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LW1.00139: Effects of atmospheric pressure non-thermal plasma treatments on aflatoxigenic fungi and its host Bo-Chen Chen This experiment tests the ability of atmospheric pressure non-thermal plasma treatments in the prevention of fungi infection. There are charged particles, electric field, radicals and UV light inside plasmas and these elements might trigger different physical or chemical effects during non-thermal plasma treatments. In this experiment, the experimental samples received indirect plasma treatments with different time duration and gas compositions which mean only the remote effects caused by plasma treatments could be seen. In this work, plasmas were produced by dielectric barrier discharge method. The operation gases were air and a mixed gas of 97{\%} He and 3{\%}O$_{2}$. After plasma treatments, fungi growth rate was observed by taking pictures and the existence of aflatoxin was qualitatively detected by black light method. The final results show that the radicals in both He/O$_{2}$ and air plasma might facilitate fungi growth rate which means peanuts received indirect plasma treatments grew fungi faster than control group. The outcomes of aflatoxin detection also shows that the fungi grown on all the sample are aflatoxigenic fungi. [Preview Abstract] |
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LW1.00140: Inactivation of Pathogenic Bacteria on Seeds by Active Oxygen Species Generated in Low-Pressure Plasma Reoto Ono, Shohei Uchida, Nobuya Hayashi, Rina Kosaka, Yasutaka Soeda The inactivation of bacteria on seeds by active oxygen species generated by a low-pressure oxygen plasma is investigated. Species of active oxygen contributing to the inactivation of bacteria are attempted to be identified. Cylindrical stainless chamber with the internal volume of 17 L is used and RF antenna is set inside the chamber. The oxygen gas pressure is 20--100 Pa. RF power of 13.56 MHz is supplied to RF antenna and CCP is generated. After irradiation, bacteria are extracted from seeds and cultivated on nutrient agars. The number of colonies on these agars is counted after 48 h incubation. The number of bacteria on seeds decreases to less than 10$^{-3}$ after plasma irradiation for 45 min comparing with that of control. The tendency of the reduction rate of bacteria on seeds has positive correlation with that of the light emission intensity of the singlet excited oxygen molecule as the oxygen gas pressure is varied. It is supposed that the singlet excited oxygen molecule would be one of the major factors for the inactivation of bacteria on seeds. [Preview Abstract] |
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LW1.00141: Disinfection effect of non-thermal atmospheric pressure plasma for foodborne bacteria Mohammad Rasel Pervez, Takanori Inomata, Tatsuo Ishijima, Makiko Kakikawa, Yoshihiko Uesugi, Yasunori Tanaka, Toshihiro Yano, Shoji Miwa, Akinori Noguchi Non-thermal atmospheric pressure plasma (NAPP) exposure can be a suitable alternative for bacteria inactivation in food processing industry. Specimen placed in the enclosure are exposed to various reactive radicals produced within the discharge chamber. It is also exposed to the periodic variation of the electric field strength in the chamber. Dielectric barrier discharge is produced by high voltage pulse ($V_{\mathrm{pp}}=$18 kV, pulse width 20 $\mu $s, repetition frequency 10 kHz) in a polypropylene box (volume$=$ 350 cm$^{3}$) using helium as main feed gas. Inactivation efficiency of NAPP depends on the duration of NAPP exposure, applied voltage pulse strength and type, pulse duration, electrode separation and feed gas composition. In this study we have investigated inactivation of \textit{Bacillus lichenformis} spore as an example of food borne bacteria. Keeping applied voltage, electrode configuration and total gas flow rate constant, spores are exposed to direct NAPP for different time duration while O$_{2}$ concentration in the feed gas composition is varied. 10 minutes NAPP exposure resulted in $\sim$ 3 log reduction of \textit{Bacillus lichenformis} spores for 1{\%} O$_{2}$ concentration (initial concentration $\sim$ 10$^{6}$ / specimen). [Preview Abstract] |
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LW1.00142: Mechanism of Growth Enhancement of Plants Induced by Active Species in Plasmas Satoshi Watanabe, Reoto Ono, Nobuya Hayashi Plant growth enhances when seeds are irradiated by plasma. However the mechanism of the growth enhancement by plasma has not been clarified. In this study, growth enhancement of plants using various active species and variation of plant cells are investigated. RF plasma is generated under conditions where pressure is 60 Pa and input electrical power is 60 W. Irradiation period varies from 0 (control) to 75 min. Air plasma shows maximum growth of plants with irradiation period of 60 min on the other hand, oxygen plasma shows the maximum growth with irradiation period of 15 min. From change of gaseous species and pressure dependence, growth enhancing factor is expected to be active oxygen species produced in plasma. According to gene expression analysis of Arabidopsis, there are two speculated mechanism of plant growth enhancement. The first is acceleration of cell cycle by gene expressions of photosynthesis and glycolytic pathway, and the second is increase of cell size via plant hormone production. [Preview Abstract] |
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LW1.00143: Simple Evaluation Method of Atmospheric Plasma Irradiation Dose using pH of Water Kazunori Koga, Thapanut Sarinont, Takaaki Amano, Hyunwoong Seo, Naho Itagaki, Yoshimichi Nakatsu, Akiyo Tanaka, Masaharu Shiratani Atmospheric discharge plasmas are promising for agricultural productivity improvements and novel medical therapies, because plasma provides high flux of short-lifetime reactive species at low temperature, leading to low damage to living body. For the plasma-bio applications, various kinds of plasma systems are employed, thus common evaluation methods are needed to compare plasma irradiation dose quantitatively among the systems. Here we offer simple evaluation method of plasma irradiation dose using pH of water. Experiments were carried out with a scalable DBD device [1-2]. 300 $\mu$l of deionized water was prepared into the quartz 96 microwell plate at 3 mm below electrode. The pH value has been measured just after 10 minutes irradiation. The pH value was evaluated as a function of plasma irradiation dose. Atmospheric air plasma irradiation decreases pH of water with increasing the dose. We also measured concentrations of chemical species such as nitrites, nitrates and H$_{2}$O$_{2}$. The results indicate our method is promising to evaluate plasma irradiation dose quantitatively.\\[4pt] [1] S. Kitazaki, et al., Curr. Appl. Phys. \textbf{14} (2014) S149.\\[0pt] [2] S. Kitazaki, et al., MRS Proc. \textbf{1469} (2012) mrss12-1469-ww0608. [Preview Abstract] |
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LW1.00144: Viability preserved capture of microorganism by plasma functionalized carbon-encapsulated iron nanoparticles Anchu Viswan, Kuniaki Sugiura, Masaaki Nagatsu Carbon-encapsulated iron nanoparticles (Fe@C NPs) were synthesized by DC arc discharge method. Carbon encapsulation makes the particles hydrophobic, however for most of the biomedical applications they need to be hydrophilic. To attain this, the particles were amino functionalized by RF plasma. Effect of gas mixture ratio (Ar/NH$_{3}$), pretreatment, post-treatment times and RF power were optimized. By varying the RF plasma conditions, the amino group population on the surface of Fe@C NPs were increased. With conventional chemical method the amino group population on particles, synthesized in different conditions was found to be ranging from 3-7 $\times$ 10$^{4}$ per particle. Bioconjugation efficiency of the nanoparticles was examined by biotin-avidin system, which can be simulated for antigen-antibody reactions. Results from the UV absorption and fluorescence spectroscopy shows increment in bioconjugation efficiency, with the increase of amino group population on the nanoparticles. After confirming the bioconjugation efficiency, the amino functionalized Fe@C NPs were modified with antibodies for targeting specific microorganisms. Our aim is to capture the microbes in viable and concentrated form even from less populated samples, with lesser time compared to the presently available methods. [Preview Abstract] |
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LW1.00145: Using advanced oxidation treatment for biofilm inactivation by varying water vapor content in air plasma Suganuma Ryota, Yasuoka Koichi Biofilms are caused by environmental degradation in food factories and medical facilities. The inactivation of biofilms involves making them react with chemicals including chlorine, hydrogen peroxide, and ozone, although inactivation using chemicals has a potential problem because of the hazardous properties of the residual substance and hydrogen peroxide, which have slow reaction velocity. We successfully performed an advanced oxidation process (AOP) using air plasma. Hydrogen peroxide and ozone, which were used for the formation of OH radicals in our experiment, were generated by varying the amount of water vapor supplied to the plasma. By varying the content of the water included in the air, the main product was changed from air plasma. When we increased the water content in the air, hydrogen peroxide was produced, while ozone peroxide was produced when we decreased the water content in the air. By varying the amount of water vapor, we realized a 99.9{\%} reduction in the amount of bacteria in the biofilm when we discharged humidified air only. [Preview Abstract] |
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LW1.00146: Proliferation enhancement of budding yeast and mammalian cells with periodic oxygen radical treatment Yosuke Mori, Jun Kobayashi, Tomiyasu Murata, Hiroshi Hahizume, Masaru Hori, Masafumi Ito Recently, nonequilibrium atmospheric-pressure plasmas have been intensively studied for biological applications. However, the each effect of species in plasmas to biological tissue has not been clarified yet because various factors exist in the plasmas. Accordingly, we have studied effects of atomic oxygen dose on cell growth such as budding yeast and mouse NIH3T3 fibroblasts of mammalian cells. Both of cells were suspended with PBS, and treated using oxygen radical source. In order to prevent the radicals from reacting with the ambient air, the treatment region was surrounded by a plastic cover and purged with Ar. The proliferative effect of $15\%$ was observed at the $O\left( {^{3}P_{j} } \right)$ dose of around $1.0\times 10^{17}$cm$^{-3}$ in NIH3T3 cells as well as in yeast cells. Moreover, periodic oxygen treatment enhanced the effect in budding yeast cells. The best interval of periodic oxygen radical treatment was around 2 hours, which is almost the same period as that of their cell cycle. With the optimum interval time, we have investigated the effect of the number of the treatments. As the number of treatments increases, the growth rate of budding yeast cells was gradually enhanced and saturated at thrice treatments. [Preview Abstract] |
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LW1.00147: Effects of solutions treated with oxygen radicals in neutral pH region on inactivation of microorganism Tsuyoshi Kobayashi, Hiroshi Hashizume, Takayuki Ohta, Kenji Ishikawa, Masaru Hori, Masafumi Ito The inactivation of microorganisms using nonequilbrium atmospheric pressure plasmas has been attracted much attention due to the low temperature processing and high speed treatment. In this study, we have inactivated E. coli suspended in solutions with neutral pH using an atmospheric-pressure oxygen radical source which can selectively supply electrically neutral oxygen radicals. E. coli cells were suspended with deionized distilled water (DDW) (pH$=$6.8) or phosphate buffered saline (PBS) (pH$=$7.4) or Citrate-Na buffer (pH$=$6.5). The treated samples were diluted and spread on nutrient agar (Nutrient Broth). They were cultured at 37$^{\circ}$ C. The inactivation effects of oxygen radicals on those cells in solutions were evaluated by colony-counting method. O2 diluted by Ar gas were employed as a working gas for the radical source. The total gas flow rate and the gas mixture ratio of O2/(Ar$+$ O2) were set at 5 slm and 0.6{\%}, respectively. The distance between the radical exit and the suspension surface were set at 10 mm. As a result, the D values for DDW(pH$=$6.8), PBS(pH$=$7.4) and Citrate-Na buffer(pH$=$6.5) were estimated to be 1.4 min, 0.9min and 16.8 min respectively. The inactivation rates in DDW, PBS were significantly different from that in Citrate-Na buffer. [Preview Abstract] |
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LW1.00148: Effect of medium treated with neutral oxygen radicals on growth of \textit{Saccharomyces cerevisiae} Jun Kobayashi, Hiroshi Hashizume, Takayuki Ohta, Masaru Hori, Masafumi Ito Recently, nonequilibrium atmospheric-pressure plasmas are expected to be applied in medical and agricultural fields. We have studied the growth effect of budding yeast cells in phosphate buffered saline (PBS(-)) using an atmospheric-pressure oxygen-radical source. From a practical application perspective, we have investigated the effect of medium treated with oxygen radicals on the growth of budding yeast in the study. The cells were suspended with yeast extract peptone dextrose (YPD) medium or PBS. The suspensions were treated with neutral oxygen radicals. Oxygen radicals were generated at an O$_{2}$/(O$_{2}+$Ar) gas flow ratio of 0.6{\%}, a total flow rate of 5 slm, and an exposure distance of 10 mm. To estimate the inactivation and the growth of yeast cells, cells were counted with the colony count method using a counting chamber and a microscope. In the case of budding yeast suspended in PBS, the growth changed from promotion to inactivation with increasing the oxygen radical treatment time. But in the case of budding yeast suspended in YPD, it didn't exhibit promotion and inactivation of the growth with oxygen radical treatment. The results indicated that some substances of YPD scavenged the growth effect of oxygen radicals. [Preview Abstract] |
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LW1.00149: PLASMA MEDICINE |
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LW1.00150: Verification of antitumor effect in vivo using nanosecond pulsed streamer discharge Kenta Yonetamari, Yuki Shirakawa, Taketoshi Akiyama, Kazue Mizuno, Ryo Ono Cancer treatment using plasma has intensively studied these days. In this work, antitumor effect by nanosecond pulsed streamer discharge was investigated. Nanosecond pulsed streamer plasma was used as a plasma source, which can generate stable streamer discharge by using a nanosecond pulsed power supply. The rod electrode of 3 mm diameter is made of copper. Its end is formed into a semispherical shape of 1.5 mm curvature. The electrode is inserted into a quartz tube (inner diameter: 4 mm, thickness: 1 mm) concentrically, so any gas can be introduced. B16F10 cells were selected to perform in vivo antitumor study. These cells were injected under the skin of leg of mice to make cancer tumor. One week later from injections, plasma was applied to the cancer tumor. Mice were randomly assigned into three groups which were one control group and two plasma treatment groups. In the control group, mice were not treated. In the plasma treatment groups, plasma with dry N2 and wet O2 as a working gas were irradiated for 5 consecutive days. Processing time was 10 min and the gap distance between the electrode and tumor was 4 mm. After 5 days plasma treatment, antitumor effect was observed. The result indicates that the streamer discharge has a potential for cancer treatment. [Preview Abstract] |
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LW1.00151: Sterilization of \textit{Bacillus atrophaeus} using OH radicals supplied by vacuum ultraviolet method Kenta Yonetamari, Yusuke Tokumitsu, Seiya Yonemori, Ryo Ono, Hachiro Yasuda, Akira Mizuno Sterilization by cold plasma has widely been performed. It is well known that reactive oxygen species (ROS) has a potential of sterilization. However, it is not clear which ROS is effective on sterilization because a lot of types of ROS are produced in plasma. In this study, sterilization effect of OH radicals by vacuum ultraviolet (VUV) method was investigated. This method utilizes photodissociation reaction to produce ROS so it can produce ROS selectively. Wet and dry helium with and without 1{\%} O2 gas was used to demonstrate sterilization effect of OH radicals. Gases were flowed in a quartz tube (inner diameter 2 mm, outer diameter 4 mm) at a flow rate of 1.5 L/min. The produced ROS flowed out of the quartz tube nozzle. A Xe2 excimer lamp emitting 172 $\pm$ 7 nm VUV light was placed parallel to the quartz tube with a distance of 8 mm. The distance between the lower end of the lamp and the nozzle of quartz tube was changed from 3 to 15 cm. As a target of sterilization, \textit{Bacillus atrophaeus} (ATCC 9372) was used. The density of OH radicals was measured using laser-induced fluorescence (LIF). As a result, sterilization using VUV method was verified. This result showed that OH radicals sterilized the bacteria. [Preview Abstract] |
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LW1.00152: The comparison of DNA damage induced by micro DBD plasma and low energy electron for curing human diseases Yeunsoo Park It is well known that low energy electrons (LEE, especially below 10 eV) can generate DNA damage via indirect action named dissociative electron attachment (DEA). We can now explain some parts of the exact mechanism on DNA damage by LEE collision with direct ionization effect when cancer patients get the radiotherapy. It is kind of remarkable information in the field of radiation therapy. However, it is practically very difficult to directly apply this finding to human disease cure due to difficulty of LEE therapy actualization and request of further clinical studies. Recently, there is a novel challenge in plasma application, that is, how we can apply plasma technology to diagnosis and treatment of many serious diseases like cancer. Cold atmospheric pressure plasma (CAPP) is a very good source to apply to plasma medicine and bio-applications because of low temperature, low cost, and easy handling. Some scientists have already reported good results related to clinical plasma application. The purposes of this study are to further find out exact mechanisms of DNA damage by LEE at the molecular level, to verify new DNA damage like structural alteration on DNA subunits and to compare DNA damage by LEE and plasma source. We will keep expanding our study to DNA damage by plasma source to develop plasma-based new medical and biological applications. We will show some recent results, DNA damage by LEE and non-thermal plasma. [Preview Abstract] |
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LW1.00153: Investigation of Sterilization Mechanism for \textit{Geobacillus stearothermophilus} Spores with Plasma-Excited Neutral Gas Kei Matsui, Noriaki Ikenaga, Noriyuki Sakudo We investigate the mechanism of the sterilization with plasma-excited neutral gas that uniformly sterilizes both the space and inner wall of the reactor chamber at atmospheric pressure. Only reactive neutral species such as plasma-excited gas molecules and radicals are separated from the plasma and sent to the reactor chamber for chemical sterilization. The plasma source gas uses humidified mixture of nitrogen and oxygen. \textit{Geobacillus stearothermophilus} spores and tyrosine which is amino acid are treated by the plasma-excited neutral gas. Shape change of the treated spore is \quad observed by SEM, and chemical modification of the treated tyrosine is analyzed by HPLC. As a result, the surface of the treated spore shows depression. Hydroxylation and nitration of tyrosine are shown after the treatment. For these reasons, we believe that the sterilization with plasma-excited neutral gas results from the deformation of spore structure due to the chemical modification of amino acid. [Preview Abstract] |
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LW1.00154: Material Compatibility of Medical Sterilizer Using Oxygen Plasma Hiroshi Tanaka, Reoto Ono, Nobuya Hayashi, Yasushi Hanada, Minoru Noda, Masaaki Goto Material compatibility of oxygen plasma sterilizer is investigated comparing with hydrogen peroxide (H$_{2}$O$_{2})$ sterilizers and a gaseous H$_{2}$O$_{2}$ sterilizer. Organic materials such as ABS, PE, PP, and PET are used as sample materials, and are irradiated by active oxygen species produced in oxygen plasma. After plasma irradiation, surface of the sample materials is observed using a scanning electron microscope and FTIR spectroscopy. Strengths of the organic materials are evaluated by the tension test. Also, H$_{2}$O$_{2}$ plasma sterilizer and a gaseous H$_{2}$O$_{2}$ sterilizer those are commercially available are utilized to compare the material compatibility, especially organic compounds. The ABS resin becomes slightly soft after irradiation by both plasmas and gaseous H$_{2}$O$_{2}$. Also, PET material becomes soften by each sterilization treatment. Decrease of peak heights of CH around 1200 and 1730 cm$^{-1}$ and increase of that of OH at 3300 cm$^{-1}$ in FTIR spectra indicates the oxidation of ABS resin by both plasma and gaseous H$_{2}$O$_{2}$. In the case of PET material, treatment by the plasma has not modified chemical composition but changed the crystal structure. The gaseous H$_{2}$O$_{2}$ is completely friendly for the PET material. [Preview Abstract] |
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LW1.00155: Spatially-Selective Membrane Permeabilization Induced by Cell-Solution Electrode Atmospheric Pressure Plasma Irradiation Shota Sasaki, Yutaro Hokari, Makoto Kanzaki, Toshiro Kaneko Gene transfection, which is the process of deliberately introducing nucleic acids into cells, is expected to play an important role in medical treatment because the process is necessary for gene therapy and creation of induced pluripotent stem (iPS) cells. However, the conventional transfection methods have some problems, so we focus attention on promising transfection methods by atmospheric pressure plasma (APP). We have previously reported that the cell membrane permeability, which is closely related with gene transfection, is improved using a cell-solution electrode for generating He-APP [1, 2]. He-APP is irradiated to the solution containing the adherent cells and delivery materials such as fluorescent dyes (YOYO-1) and plasmid DNA (GFP). In case of YOYO-1 delivery, more than 80{\%} of cells can be transferred only in the plasma-irradiated area and the spatially-selective membrane permeabilization is realized by the plasma irradiation. In addition, it is confirmed that plasmid DNA is transfected and the GFP genes are expressed using same APP irradiation system with no obvious cellular damage. \\[4pt] [1] S. Sasaki, M. Kanzaki, and T. Kaneko, Appl. Phys. Express 7 (2014) 026202.\\[0pt] [2] T. Kaneko, S. Sasaki, Y. Hokari, S. Horiuchi, R. Honda, and M. Kanzaki, Biointerphases 10 (2015) 029251. [Preview Abstract] |
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LW1.00156: Measurement of plasma-generated RONS in the cancer cells exposed by atmospheric pressure helium plasma jet Hea Min Joh, Eun Jeong Baek, Sun Ja Kim, Tae Hun Chung The plasma-induced reactive oxygen and nitrogen species (RONS) could result in cellular responses including DNA damages and apoptotic cell death. These chemical species, O, O$_{\mathrm{2}}^{\mathrm{-}}$, OH, NO, and NO$_{\mathrm{2}}^{\mathrm{-}}$, exhibit strong oxidative stress and/or trigger signaling pathways in biological cells. Each plasma-generated chemical species having biological implication should be identified and quantitatively measured. For quantitative measurement of RONS, this study is divided into three stages; plasma diagnostics, plasma-liquid interactions, plasma-liquid-cell interactions. First, the optical characteristics of the discharges were obtained by optical emission spectroscopy to identify various excited plasma species. And the characteristics of voltage-current waveforms, gas temperature, and plume length with varying control parameters were measured. Next, atmospheric pressure plasma jet was applied on the liquid. The estimated OH radical densities were obtained by ultraviolet absorption spectroscopy at the liquid surface. And NO$_{\mathrm{2}}^{\mathrm{-}}$ is detected by Griess test and compared between the pure liquid and the cell-containing liquid. Finally, bio-assays were performed on plasma treated human lung cancer cells (A549). Intracellular ROS production was measured using DCF-DA. Among these RONS, productions of NO and OH within cells were measured by DAF-2DA and APF, respectively. The data are very suggestive that there is a strong correlation among the production of RONS in the plasmas, liquids, and cells. [Preview Abstract] |
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LW1.00157: Sterilization Performance and Material Compatibility of Sterilizer for Dental Instruments using RF Oxygen Plasma Yasuhiro Sakai, Zhen Liu, Nobuya Hayashi, Masaaki Goto The sterilization performance and material compatibility of low-pressure RF plasma sterilization method for dental instruments were investigated. RF electrode used in this experiment has been optimized for sterilization of dental instruments. The vial-type biological indicator (BI) simulating tiny space of dental instrument was used for evaluation of the sterilization performance. The pressure in the stainless chamber was fixed at 60 Pa. Sterilization of BI was achieved in shortest time 40 min at 80 W, and the sterilization effect was confirmed using three BIs. Light emission spectra of oxygen plasma indicated that production of atomic oxygen and excited oxygen molecule are maximum at pressure of 20 Pa and 200 Pa, respectively. Sterilization results of BIs indicated that successful rate increases with the oxygen pressure towards 200 Pa. Therefore, the excited oxygen molecule is deduced to be a major factor of the sterilization of BI. Surface morphology of dental instruments such as diamond bar was evaluated using scanning electron microscope (SEM). The deterioration of fine crystals of diamond bar has not observed after the plasma irradiation for 120 min with RF input power was 60W and pressure was 200 Pa. [Preview Abstract] |
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LW1.00158: Synthesis of indium-containing nanoparticles using plasmas in water to study their effects on living body Takaaki Amano, Kazunori Koga, Thapanut Sarinont, Hyunwoong Seo, Naho Itagaki, Masaharu Shiratani, Satoshi Kitazaki, Miyuki Hirata, Yoshimichi Nakatsu, Akiyo Tanaka Nanoparticles can be employed for biomedical applications such as biomarkers, drug delivery systems, and cancer therapies. They are, however, pointed out their adverse effects on human body. Here, we synthesed indium-containing nanoparticles using discharge plasmas with indium electrodes immersed in DI water and administrated nanoparticles to rats to analyze their kinetics in living body. The discharge power was 5.1 W. The electron density is 5x10$^{17}$/cm$^{3}$ deduced from Stark broadening of hydrogen lines. TEM observation shows the mean size of primary nanoparticles is 7 nm. The nanoparticles are indium crystalline and indium hydroxide crystalline. The synthesized nanoparticles and purchased nanoparticles (In$_{2}$O$_{3}$, \textless 100nm) were administrated to rats using subcutaneous injection. Indium of 166.7 g/day (synthesized) and of 27.8 g/day (purchased) are detected from the urine at 12 weeks after the administration. Synthesized nanoparticles dispersed in water are useful for analyzing kinetics of nanoparticles in living body. Work partly supported by KAKENHI. [Preview Abstract] |
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LW1.00159: Analysis of non-thermal plasma-induced cell injury in human lung cancer cell lines Hirofumi Kurita, Kaori Sano, Motoi Wada, Kazue Mizuno, Ryo Ono, Hachiro Yasuda, Kazunori Takashima, Akira Mizuno Recent progress of biomedical application of atmospheric pressure plasma shows that the biological effects are mainly due to reactive oxygen and nitrogen species (RONS) in liquid produced by the plasma exposure. To elucidate the cellular responses induced by exposure to the plasma, we focused on identification and quantification of reactive chemical species in plasma-exposed cell culture medium, and cell injury in mammalian cells after treatment of the plasma-exposed medium. In this study, we examined human lung cancer cell lines. The contribution of H$_{\mathrm{2}}$O$_{\mathrm{2}}$ to the cellular responses was considered. Here, an atmospheric pressure plasma jet (APPJ) sustained by a pulsed power supply in argon was used. After APPJ exposure to cell culture medium, RONS detection in liquid was conducted. It showed that OH radical, ONOO$^{\mathrm{-}}$, NO$_{\mathrm{2}}^{\mathrm{-}}$, NO$_{\mathrm{3}}^{\mathrm{-}}$, and H$_{\mathrm{2}}$O$_{\mathrm{2}}$ were produced in the plasma-exposed medium. Cellular responses of human lung cancer cell lines to the plasma-exposed medium in a concentration-dependence manner were also studied. It showed that the plasma-exposed medium and the H$_{\mathrm{2}}$O$_{\mathrm{2}}$ treatment gave similar reduction in viability and induction of apoptosis. [Preview Abstract] |
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LW1.00160: The effect of the suspension cells in plasma gene transfection method Yuki Isozaki, Koki Nakano, Yoshihisa Ikeda, Hideki Motomura, Yugo Kido, Susumu Satoh, Kunihide Tachibana, Masafumi Jinno Plasma gene transfection method is a unique technique for introducing nucleic acids into cells by using plasma irradiation. In our previous works, plasma gene transfection method was performed for the adherent cells, e.g. COS-7 cells, and the influence of plasma on gene transfection has been investigated. As a next step for plasma medicine, transfection to much more various kinds of target cells is required. In this study, the authors attempted gene transfection to two kinds of suspension and four kinds of adherent cells. Although the transfection ratios to the suspension cells were low, transfection to all the kinds of cells were validated. To upregulate the transfection ratio for suspension cells, the authors are validating related factors by plasma irradiation. [Preview Abstract] |
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LW1.00161: Investigation on Large Molecule Permeation through Liposome Lipid Bilayer Induced by Microplasma Irradiation Hidenori Nagaiwa, Daijiro Aibara, Yoshihisa Ikeda, Hideki Motomura, Yugo Kido, Susumu Satoh, Kunihide Tachibana, Masahumi Jinno The authors have been developing a novel gene transfection method using microplasma irradiation. In order to clarify the mechanism of large molecule permeation process through the lipid bilayer, plasma induced outflow of hydrophilic fluorescent dye molecules, which were encapsulated in the liposome, was observed. By microplasma irradiation on the liposome suspension, the dyes flowed out from the inside of the liposomes. The outflow of the dyes was enhanced by longer plasma irradiation time. Investigation of the outflow mechanism, i.e. permeation enhancement of the lipid bilayer or burst of the liposome, is under progress. [Preview Abstract] |
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LW1.00162: Influence of the H$_{2}$O$_{2}$ in the plasma gene transfection method Masanori Kimura, Hiroki Tachibana, Yuki Ohno, Yoshihisa Ikeda, Hideki Motomura, Yugo Kido, Susumu Satoh, Kunihide Tachibana, Masafumi Jinno Gene transfection is the process of deliberately introducing nucleic acids into cells. The authors have been developing a novel gene transfection method using microplasma irradiation (plasma gene transfection method). Our previous study shows that long life chemically reactive species contribute to gene transfection, which induce the transfection at least 60~s after plasma irradiation (after effect). In order to clarify the key reactive species which is effective on the after effect, the effect of H$_{2}$O$_{2}$ addition after plasma irradiation was investigated. Addition of H$_{2}$O$_{2}$ at 1/1000$-$1~ppm after plasma irradiation did not largely affect or slightly decease the transfection ratio, whereas the H$_{2}$O$_{2}$ concentration induced by plasma irradiation is estimated as 2.7~ppb after dilution by the medium. It is found that the H$_{2}$O$_{2}$ is not main species for the after effect. [Preview Abstract] |
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LW1.00163: Effect of the cell temperature in the plasma gene transfection Yoshihisa Ikeda, Kunimori Manabe, Yuki Isozaki, Hideki Motomura, Yugo Kido, Susumu Satoh, Kunihide Tachibana, Masafumi Jinno The authors study effect of the cells temperature in the plasma gene transfection by changing temperature of the GND electrode from 5\ $^\circ$C and to 55\ $^\circ$C to identify the mechanism of transfection by plasma. By increasing the GND electrode temperature, the transfection ratio increased up to 45\ $^\circ$C and then decreased at higher temperature. The best fitting curve indicates that the optimum temperature for the maximum transfection ratio, which is 1.25 times higher than that at room temperature, is approximately 40\ $^\circ$C. In general, activation of cells will be also maximum around this temperature. Therefore, it is suggested that the cell activation enhances the gene transfection ratio under plasma irradiation. [Preview Abstract] |
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LW1.00164: Characteristics of Surface Sterilization using ECR Plasma Akira Yonesu, Kazufumi Hara, Tatsuya Nishikawa, Nobuya Hayashi Plasma sterilization techniques have superior characteristics such as a short treatment times, non-toxicity and low thermal damages on the sterilized materials. In plasma sterilization, microorganisms can be sterilized by active radicals, energetic charged particles, and vacuum UV radiation. The influence of each factor depends on the plasma operating parameters. Microwave discharges under the electron cyclotron resonance (ECR) condition produce higher electron temperature and density plasma as compared with other plasma generation techniques. In the present study, characteristics of surface sterilization using ECR plasma have been investigated.The experiment was performed in the vacuum chamber which contains a magnet holder. A pair of rectangular Sm-Co permanent magnets is aligned parallel to each other within the magnet holder. The region of the magnetic field for ECR exists near the magnet holder surface. When the microwave is introduced into the vacuum chamber, a ECR plasma is produced around surface of the magnet holder. High energy electrons and oxygen radicals were observed at ECR zone by electric probe method and optical spectroscopic method. Biological indicators (B.I.) having spore of 10$^{\mathrm{6}}$ was sterilized in 2min for oxygen discharge. The temperature of the B.I. installation position was about 55${^\circ}$. The sterilization was achieved by the effect of oxygen radicals and high energy electrons. [Preview Abstract] |
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LW1.00165: PLASMAS FOR NANOTECHNOLGIES, FLEXIBLE ELECTRONICS AND OTHER EMERGING APPLICATIONS |
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LW1.00166: Domain control of ZnO nanoparticles in a coaxial gas-flow pulse Ar/O$_{2}$ plasma Satoru Iizuka, Hiroki Shirahata A limited area, to which ZnO nanoparticles are selectively adhered, is called a domain. Formation of the domain was controlled by using a coaxial gas-flow pulse Ar/O$_{2}$ plasma. It was found that the mechanism of domain formation was closely related to the initial surface condition of Si substrate. Especially, the cleaning process was crucial. Here, we employed a patterning of the domain by using a fine mesh as a template. The formation processes were estimated by SEM and EDX. The technique developed here will be applied to a selective nanoparticle patterning. [Preview Abstract] |
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LW1.00167: Characterization of self-assembled silver pattern forming in argon and ammonia mixed atmospheric pressure plasma Naoya Kihara, Ella Blanquet, Yu Hiraoka, Osamu Sakai Self-assembly fractal-like silver pattern was observed when the silver nitrate solution was dried with the gas flow of argon and ammonia mixed atmospheric plasma. This process can generate hydrazine, which is a powerful reductive agent, and silver particles are deposited from silver nitrate self-assembly [1] and form fractal-like pattern in sub-$\mu $m order. This pattern shows abnormal optical response, so our self-assembly plasma process will be likely to bring a good method to make optical metamaterials because of its simplicity. In addition, we proposed that this process is applicable for widely sensitive metamaterials process, since we made sub-$\mu $m and several ten micrometers mingled microstructure through the plasma process with the use of micro particles. We diagnosed the characteristics of this typical pattern by Fourier transform infrared spectroscopy and numerical simulation, and confirmed that the pattern was widely sensitive from mid-infrared to far-infrared region. We aim at controlling the typical response phenomena and making widely sensitive optical metamaterials with changing deposition condition. \\[4pt] [1] K. Urabe, Y. Hiraoka, and O. Sakai: Plasma Sources Sci. Technol. 22 (2013) 032003. [Preview Abstract] |
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LW1.00168: Effects of Flux and Energy of Neutral Beam on Hydrogenation of Graphene Takeru Okada, Seiji Samukawa Hydrogen modification, hydrogenation, of graphene, has attracted due to the possibility of hydrogen storage. Chemisorbed hydrogen has strong interaction with graphene surface and sp3 bond forms. Surprisingly, ideal structure of graphene shows reversible absorption of hydrogen and it leads to effective designing of hydrogen storage material. In this paper, we have demonstrated neutral beam (NB) technique for hydrogenation of graphene instead of conventional plasma method. NB system consists of a plasma generation chamber and a process chamber, which are separated by a carbon plate with many apertures. The charged particles can be effectively neutralized by collision with the sidewall of the apertures when passing through them to the process chamber. Development of the D-band and blue shift of G-band were observed after hydrogen NB irradiation by Raman spectroscopy. FTIR analysis reveals CH bending mode was appeared and it depends on beam energy, thus CH formation has reaction threshold and potential to control it. In addition, it is shown that beam flux affects hydrogenation and additional effect is also included in reaction process. We believe our investigation will provide development of hydrogenated graphene applications. [Preview Abstract] |
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LW1.00169: Oxygen sensitivity of zinc oxide nanoparticles produced via laser-ablated plasma in pressurized liquid Taku Goto, Yoshiki Shimizu, Tsuyohito Ito While traditional semiconductor oxygen sensor operate only with elevated temperature ($\agt$ 700 K), the room-temperature operation of the ZnO oxygen sensors have been demonstrated with the help of UV light irradiation. Especially, ZnO nanotubes and nanoparticles have attracted much attentions as highly sensitive oxygen sensors and photodetectors. To the best of our knowledge, the reported works of gas sensors with ZnO nanostructures have been mostly intended for revealing effects of the morphology/shape and the size of the nanostructures. For further improvements of the ZnO-based gas sensors, it is probably required to understand effects of microscopic structures, such as densities of various defects. In this study, we synthesized the ZnO nanoparticles with various defects by means of laser-ablated plasma in pressurized water-ethanol mixture. The results indicate that the defects in ZnO affect oxygen sensitivity, and especially VO$+$ defects seem to be mostly responsible for the resistance change of ZnO nanoparticles. We demonstrate that partial oxygen pressure can be measured with high sensitivity. [Preview Abstract] |
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LW1.00170: Plasma-induced processing in microdroplets for nanoparticles synthesis Masanao Tsumaki, Yoshiki Shimizu, Tsuyohito Ito Plasma processing in microdroplets is studied, as the solute of organic compounds in the microdroplets is a raw material for nanoparticles synthesis. Synthesis of ZnO nanoparticles with wurtzite structure and control of their size distribution with regulating the zinc acetate (Zn(Ac)$_2$) solution concentration are achieved. The plasma is generated by means of dielectric barrier discharges in He gas flow, and the generated particles are analyzed by photoluminescence spectroscopy, scanning electron microscopy, and transmission electron microscopy. The size distribution shifted with the increase of Zn(Ac)$_2$ concentration, and the average sizes are expected by assuming one ZnO nanoparticle is formed from one microdroplet with known Zn(Ac)$_2$ density. The properties of nanoparticles are independent of the solution concentration within the tested range (0.5-2 mM), except of their sizes. The results strongly suggest that one microdroplet is a closed reaction area, thus providing certain controllability of the generated nanoparticles. [Preview Abstract] |
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LW1.00171: Plasma requirements for vertically aligned carbon nanowalls synthesis Lucia Bonova, Jana Bohovicova, Juraj Halanda, Martin Muska, Marcel Mesko Graphene related nanostructures have large potential in energy storage applications because of their unique physical and chemical properties. Carbon nanowalls (CNWs) are practical realization of graphene containing nanostructures. CNWs are two-dimensional carbon structures that consist of stacked graphene sheets standing vertically on substrates. Vertically aligned carbon nanowalls were synthetized by atmospheric direct current plasma enhanced chemical vapor deposition. The CNWs nucleation and aligned mechanism on catalytically active surfaces were revealed. Importance of plasma conditions for vertically aligned CNWs synthesis is evidenced by analyzing both outside and inside growth area. [Preview Abstract] |
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LW1.00172: Plasma Properties of Superimposed Dual Frequency Inductively Coupled Plasma Source Tae Hyung Kim, Seung Min Lee, Chul Hee Lee, Jeong Oun Bae, Kyong Nam Kim, Geun Young Yeom Plasma characteristics of internal linear inductively coupled plasma sources using dual frequency composed 2 and 13.56 MHz were investigated. Improved plasma characteristics such as higher plasma density, lower electron temperature, and plasma non-uniformity were observed with the dual frequency. Therefore, by using the dual frequency to the U-shaped ICP source, not only the plasma density but also plasma uniformity could be improved in addition to the decrease of possible damage to the substrate. [Preview Abstract] |
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LW1.00173: The characteristics of the MWCNT after treatment with inductively coupled plasma Hunsu Lee, Wooyoung Kim, Yong Chae Jung The treatment of the carbon nanotubes with plasma is being reported as an effective method to enhance the dispersion properties and functionalization. The characteristics of carbon nanotube such as the degree of defect of atomic composition differs according to the plasma source used for the treatment and the difference affect the electrical or mechanical properties of the composite materials using the nanotube as filler. In this poster, the effect of plasma treatment with capacitively coupled plasma and inductively coupled plasma on the characteristics and the measured plasma parameters is discussed. The ion bombardment energy on the surface of the nanotube, electron temperature and electron density affected the characteristics of the carbon nanotube and the control of the carbon nanotube composite is thought to be enabled with proper selection of the plasma source for the treatment. [Preview Abstract] |
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LW1.00174: Plasma -- enhanced dispersion of metal and ceramic nanoparticles in polymer nanocomposite films Paul Maguire, Yazi Liu, Sadegh Askari, Jenish Patel, Manuel Macia-Montero, Somak Mitra, Richao Zhang, Dan Sun, Davide Mariotti In this work we demonstrate a facile method to synthesize a nanoparticle/PEDOT:PSS hybrid nanocomposite material in aqueous solution through atmospheric pressure direct current (DC) plasma processing at room temperature. Both metal (Au) and ceramic (TiO2) nanoparticle composite films have been fabricated. Nanoparticle dispersion is enhanced considerable and remains stable. TiO$_{\mathrm{2}}$/polymer hybrid nanoparticles with a distinct core shell structure have been obtained. Increased nanoparticle/PEDOT:PSS nanocomposite electrical conductivity has been observed. The improvement in nanocomposite properties is due to the enhanced dispersion and stability in liquid polymer of microplasma processed Au or TiO$_{\mathrm{2}}$ nanoparticles. Both plasma induced surface charge and nanoparticle surface termination with specific plasma chemical species are thought to provide an enhanced barrier to nanoparticle agglomeration and promote nanoparticle-polymer bonding. This is expected to have a significant benefit in materials processing with inorganic nanoparticles for applications in energy storage, photocatalysis and biomedical sensors. [Preview Abstract] |
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LW1.00175: Characterization of a K-Band Plasma Controlled Photonic Crystal David Biggs, Mark Cappelli The effect of a low-pressure plasma column on a resonant cavity in a miniature photonic crystal is studied experimentally and computationally. The photonic crystal is created using a square array of alumina rods with the center rod removed to create the resonant cavity. Out of plane radiative losses are minimized by a copper waveguide on either side of the photonic crystal. The plasma column is formed by a kHz discharge in argon gas at \textless 1 Torr. The bandgap and defect state properties of the photonic crystal with and without a plasma column are measured using a vector network analyzer. The time resolved history of the plasma discharge is measured with a crystal detector. The experiments are compared with simulations using a finite difference time domain electromagnetic solver and a simple Drude model of the plasma column. [Preview Abstract] |
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LW1.00176: Releasing of Sputtered Au Film by Dissolving Sacrificial Layer and Its Self-Standing on Perforated Substrate Yu Miyamoto, Yuma Fujii, Masafumi Yamano, Toru Harigai, Yoshiyuki Suda, Hirofumi Takikawa, Mamiko Nishiuchi, Hironao Sakaki, Kiminori Kondo Free-standing thin films such as diamond-like carbon (DLC) and gold (Au) have been attracted increasing interests as film targets used in the laser-driven ion acceleration experiment [1]. One of the methods to make the free-standing thin film is to use a soluble sacrifice layer [2]. In this study, the fabrication technique of self-standing Au thin film is presented. Gelatin, oblate, silk fibroin, and NaCl were examined as a. Au thin films were deposited by DC plasma sputtering on sacrifice layers. The gelatin and oblate were used as the sacrificial layer and the supporting substrate. Silk fibroin was coated on glass substrates by a spin coater. The NaCl sacrificial layers were deposited on flat Si substrates by the vacuum vapor deposition system. Sputtered Au thin films were released by immersing the substrates in purified water. Self-standing Au thin films were fabricated by scooping up the released Au thin film on a perforated substrate. The highest quality of the self-standing Au thin film was achieved by using NaCl sacrificial layer. \\[4pt] [1] M. Nishiuchi: J. Plasma Fusion Res., 88, 5-12 (2012)\\[0pt] [2] F. Gao, et al.: Nucl. Instr. and Meth. A, 577, 397-401 (2007) [Preview Abstract] |
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LW1.00177: A study of a split ring resonator response to free-space Ku band excitation in the presence of a gap plasma discharge Jack Goodwin, Roberto Colon Quinones, Fabio Righetti, Ben Wang, Mark Cappelli Split-ring resonators are commonly used elements in metamaterials. Their L-C resonance drives a permeability that can take on negative values affording novel interactions with free space radiation. The capacitance is partially dictated by the split ring gap. In this study, we examine both theoretically and experimentally, the electromagnetic response of a split ring resonator, and arrays of resonators, to incident Ku band radiation under conditions in which a gas discharge or laser-produced plasma is generated in proximity of the gap. The resonance is found to shift towards higher frequencies, consistent with what is expected from simple theoretical modeling. [Preview Abstract] |
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LW1.00178: Atmospheric Pressure Micro-Thermal-Plasma-Jet Crystallization of Amorphous Silicon Strips for High-Performance Thin Film Transistor Fabrication Seiji Morisaki, Taichi Nakatani, Ryota Shin, Seiichiro Higashi Zone melting recrystallization (ZMR) of amorphous silicon (a-Si) strips by micro-thermal-plasma-jet (u-TPJ) irradiation is quite effective to suppress grain boundaries (GBs) except sigma 3 coincidence site lattice (CSL). Intra-grain defects in 1 $\mu$m wide strips were significantly reduced by suppressing the agglomeration of molten Si with low temperature condition around melting point of crystalline Si. Thin film transistors (TFTs), using optimized ZMR condition by scanning speed of 1500 mm/s demonstrated extremely high performance with field effect mobility ($u_{\mathrm{FE}})$ of 443 cm$^{2}$/Vs and swing factor ($S)$ of 210 mV/dec. [Preview Abstract] |
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LW1.00179: DNA Microarray Analysis of Gene Expression in Yeast, \textit{Saccharomyces cerevisiae}, responses to Floating-Electrode Dielectric Barrier Discharge Plasma Irradiation. Yoshihito YAGYU, Nobuya Hayashi, Yuta Hatayama, Takashi Yamasaki, Tamiko Ohshima, Masahiro Koshimura, Taiki Miyamoto, Hiroharu Kawasaki, Takeshi Ihara, Yoshiaki Suda Effect of plasma irradiation for an application of plasma medicine has been investigated, and active species generated in plasma probably play an important part in a reaction between plasma and biological subjects relating to living organisms. In this study, gene expression variation of yeast, \textit{Saccharomyces cerevisiae}, treated by floating-electrode dielectric barrier discharge (FE-DBD) as an atmospheric plasma source was analyzed by DNA microarray method. As a result, it has been found that the variance of gene expression caused by FE-DBD plasma irradiation was detected. The variance of gene expression will be investigated by using a data on a biochemical pathways for analyzing a detail about effect of plasma irradiation to living organisms. [Preview Abstract] |
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