Bulletin of the American Physical Society
70th Annual Gaseous Electronics Conference
Volume 62, Number 10
Monday–Friday, November 6–10, 2017; Pittsburgh, Pennsylvania
Session JW1: Gas Phase Plasma Chemistry I |
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Chair: Sergey Macheret, Purdue University Room: Salon D |
Wednesday, November 8, 2017 8:00AM - 8:15AM |
JW1.00001: Global model of Negative Hydrogen Ion Source. Sergey Averkin, John Cary, Thomas Jenkins, Scott Kruger, Madhusudhan Kundrapu, Seth Veitzer A global model is applied to investigate complicated chemistry in a Negative Hydrogen Ion Source in preparation for the spatially varying simulations using USim, a multi-species fluid code. The global model includes electrons, neutral hydrogen molecules with all vibrational states ($\mbox{H}_{2} (v))$, hydrogen atoms in the first 3 electronic states ($\mbox{H(n)})$, and ground state ions ($\mbox{H}^{+}$, $\mbox{H}_{2}^{+} $, $\mbox{H}_{3}^{+} $, and $\mbox{H}^{-})$. The model includes a comprehensive set of surface and volume chemical reactions. In the global model, steady state species continuity equations, electron energy and total energy equations, heat transfer to walls, and quasineutrality are solved simultaneously in order to calculate number densities and temperatures of plasma components in the discharge over a wide range of parameters (pressures and absorbed powers). These simulations allow one to extract the most important species and reactions in a Negative Hydrogen Son Source. [Preview Abstract] |
Wednesday, November 8, 2017 8:15AM - 8:30AM |
JW1.00002: Collisional radiative model for Ar/O2 plasma with reliable fine structure resolved cross sections . Priti Priti, Reetesh Gangwar, Rajesh Srivastava A collisional radiative (CR) model has been developed for Ar/O$_{\mathrm{2}}$ mixture plasma. Here we extend our previous CR model for pure Ar plasma [1] by including the quenching of the excited Ar atoms with O$_{\mathrm{2\thinspace }}$along with the other processes \textit{viz.} radiative population transfer, electron impact excitation and ionization. Since electron collision processes play vital role, a complete data set obtained using relativistic distorted wave theory is used. Present work is in the light of recent measurement [2] on Ar/O$_{\mathrm{2}}$(0-5{\%}) mixture plasma at 2 Torr pressure. Diagnostics have been done by optimizing the normalized intensities obtained from this model with the measured intensities [2] for different transitions between fine stricture levels. The population densities of fine structure states of Ar(1s) are obtained and compared with the measurements [2] at different O$_{\mathrm{2}}$ fractions. The electron temperature is found to increase (0.9 to 1.8eV) with O2 fraction (0-5{\%}). \begin{enumerate} \item Dipti \textit{et. al.,} \textit{Eur. Phys. J. D} \textbf{67} 203, 2013 \item Jogi \textit{et. al,} \textit{J. Phys. D: Appl. Phys.} \textbf{47} 335206,2014. \end{enumerate} [Preview Abstract] |
Wednesday, November 8, 2017 8:30AM - 8:45AM |
JW1.00003: A zero dimensional model of microwave induced coaxial surface wave discharge fed with hexamethyldisiloxane/oxygen Efe Kemaneci, Ralf Peter Brinkmann, Felix Mitschker, Peter Awakowicz A zero-dimensional global model is developed to analyse a microwave induced coaxial discharge of examethyldisiloxane/oxygen. The wall flux is analytically estimated and the model is validated by comparing against a variety of measurements for a feeding gas of argon or oxygen. Ion wall flux significantly contributes to the net loss rate of the positive ions. A primary chemical kinetics is added to the oxygen study to investigate the characteristics of the plasma with admixture ratio of 50:100 (HMDSO/O$_2$). Even though the dominant background gas is oxygen, the simulations suggest that the highest positive ion concentration belongs to Si$_2$OC$_5$H$_{15}^{+}$ that is also confirmed by measurements. The simulation results are compared with existing measurements and an agreement is obtained. [Preview Abstract] |
Wednesday, November 8, 2017 8:45AM - 9:00AM |
JW1.00004: Vibrational excitation and temperature evolution in a pulsed CO2 discharge Olivier Guaitella, Ana-Sofia Morillo-Candas, David Yap, Cyril Drag, Jean-Paul Booth, Bart Klarenaar, Richard Engeln, Marija Grofulovic, Tiago Silva, Vasco Guerra In spite of the abundant literature on CO2 lasers, many energy transfer coefficients are still missing to accurately describe the vibrational kinetic in CO2 and CO2 containing plasmas that are investigated for CO2 recycling technologies. A set of complementary measurements is performed in a simple pulsed glow discharge in order to provide constraints to kinetic models of such plasmas. Time resolved in situ FTIR is used to obtain vibrational temperature of CO2 and CO during plasma pulses and the afterglow. High spectral resolution TALIF gives simultaneously O atoms density and also their temperature from the Doppler broadened profile of the fluorescence line of O atoms. The time evolution of gas temperature is obtained from Raman scattering measurements. The knowledge of gas temperature, vibrational temperature, radical and molecules densities, and electric field in the same plasma cell allow exhibiting the influence of surface properties on the plasma dynamics as well as detailed comparison with kinetic modeling of the gas phase. In addition of pure CO2 plasma, several experiments are carried out in CO2/N2 and CO2/CH4 in contact with catalytic materials for molecules synthesis purpose. [Preview Abstract] |
(Author Not Attending)
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JW1.00005: Selfconsistent Vibrational and Free Electron Kinetics in Reacting CO$_2$/CO Plasmas Lucia Daniela Pietanza, Gianpiero Colonna, Mario Capitelli A self-consistent time--dependent model based on the coupling between the Boltzmann equation for free electrons, the non equilibrium vibrational kinetics for the asymmetric mode of CO$_2$ and for CO vibrational levels and simplified global models for the dissociation and ionization plasma chemistry is applied to conditions met under pulsed microwave, dielectric barrier discharge and nanosecond pulsed discharges. The results show that, in MW conditions, large concentrations of vibrational excited states are generated, which affect the electron energy distribution function through superelastic vibrational collisions. Moreover, in discharge and post-discharge conditions, the vibrational distribution functions of both CO$_2$ and CO are characterized by plateaux due to V-V up pumping mechanism. These plateaux promote dissociation processes by pure vibrational mechanisms, which can overcome the electron impact dissociation rates. The eedf in post-discharge conditions shows characteristic plateaux due to superelastic processes involving the electronic excited states of the species of both CO$_2$ and CO species. [Preview Abstract] |
Wednesday, November 8, 2017 9:15AM - 9:30AM |
JW1.00006: Reaction DB construction of Perfluorocarbons for Plasma process simulation Satoshi Nakamura, Rei Sakuma, Sun-Taek Lim, Shogo Sakurai, Hiroyuki Kubotera, Kiyoshi Ishikawa, Keun-Ho Lee Plasma process simulation plays an important role for the development of plasma etching process in the semiconductor industry. Although the results of the simulation are primarily depends on DB of the cross section and/or reaction rate for the scattering between molecules and electron in the gas phase, their data are still insufficient. In this presentation, we propose a semi-empirical method to evaluate cross-sections for some perfluorocarbons which are widely employed in the plasma etching process. There are various established methods to calculate cross sections for impact dissociation via excitation process, dissociative/non-dissociative ionization, and dissociative electron attachment except for non-dissociative electron attachment (NDEA). Using specific relation between peak value and peak energy of the cross section from experimental data for NDEA of some perfluorocarbons (CF$_4$, C$_2$F$_6$, C$_3$F$_8$, and so on), and combined with first-principles calculations we obtained reasonable cross-sections for NDEA of molecules whose experimental data are absent. This approach will be applied for other gases and other types of reactions without NDEA to increase DB for Plasma process simulation. [Preview Abstract] |
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