Bulletin of the American Physical Society
62nd Annual Gaseous Electronics Conference
Volume 54, Number 12
Tuesday–Friday, October 20–23, 2009; Saratoga Springs, New York
Session HT2: DC, Pulsed, RF and Microwave Glows |
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Chair: Siva Kanakasabapathy, IBM Room: Saratoga Hilton Ballroom 2 |
Tuesday, October 20, 2009 1:30PM - 1:45PM |
HT2.00001: Temporal variation of plasma density in atmospheric-pressure pulsed-microwave plasma Hirotaka Toyoda, Haipeng Yang, Tatsuo Ishijima Atmospheric pressure plasma is often produced by pulsed mode at a power duration less than a few tens $\mu $s so as to suppress transition from non-equilibrium to equilibrium plasma. Taking account for the time scale of plasma density increase (a few to 10 $\mu $s) after the plasma ignition, the plasma density is considered to be strongly time-dependent during the pulsed atmospheric pressure plasma. In this study, temporal variation of H$_{\beta}$ spectra in atmospheric-pressure pulsed-microwave plasma is investigated by a gated optical multichannel analyzer (OMA) to give insight into the temporal variation of plasma density as well as the electric field. From the H$_{\beta}$ line-width measurements for different polarizations, i.e., polarization parallel and perpendicular with respect to the applied electric field, contribution of Stark splitting due to external electric field is discriminated from the measured H$_{\beta}$ line width. Line broadening due to the Stark splitting is clearly observed immediately after the plasma ignition, suggesting that the externally applied field penetrates into the plasma at this stage and that such influence must be subtracted for the precise plasma density measurement by Stark broadening. [Preview Abstract] |
Tuesday, October 20, 2009 1:45PM - 2:00PM |
HT2.00002: The rf Micro-Hollow Device P.D. Maguire, C.M.O. Mahony, J. Greenan, T. Gans, D. O'Connell, W.G. Graham The rf Micro-Hollow Device (rfMHD) is a new micro-plasma source with which we aim to provide sub 10 micron plasmas and densities $>$10$^{22 }$m$^{-3}$. Applications include targeted processing for electronic {\&} bio-materials, gas sensors and light sources. The micron-scale dimensions and near atmospheric pressure operation give new physics at turn on and during steady state operation. RfMHDs of 25 microns diameter have been demonstrated[1]; they ignite readily and operate stably at powers less than 10W. The rfMHD device will be introduced and its operation described. Results from electrical and optical measurements {\&} their analysis will be presented. Potential processes contributing to ignition {\&} sustainment will be discussed. The prospects of operating with smaller source diameters {\&} the science required to describe operation at these reduced scales will be addressed. The rfMHD will be presented in the context of biomedical applications currently of interest to this centre.\\[4pt] [1] Mahony, Gans, Graham, Maguire {\&} Petrovic, 2008 \textit{Appl Phys Lett} \textbf{93} 011501 [Preview Abstract] |
Tuesday, October 20, 2009 2:00PM - 2:15PM |
HT2.00003: Temporal and Spatial evolution of the EEP$f$ and the Discharge Mechanism in a Microwave Surface-Wave Plasma Ron Bravenec, Jianping Zhao, Merritt Funk, Lee Chen, Toshihisa Nozawa Surface-wave plasma excited at 2.45GHz by the radial line slot antenna (RLSA) has been used for plasma CVD, film-growth and more recently, etching applications. Its noted performance advantage is thought to be due to a low $T_{e}$ quiescent plasma in the wafer-region. 2-D particle-in-cell (PIC) numerical experiments are used to elucidate its energy-coupling mechanism in sustaining plasma ionization. Temporal evolution from power onset through ignition to steady state reveals E-field amplification under the \textit{$\omega $}$_{P}$=\textit{$\omega $} resonance. Consequent Langmuir waves serve to complete the ignition process through Landau damping on the fast electrons. Approach toward steady state results from a continuation of the \textit{$\omega $}$_{P}$=\textit{$\omega $} resonance or heating by the surface wave's ponderomotive force depending on the density. The steady-state EEP$f$ near the dielectric plate exhibits a beam-like component which is verified by probe measurements. Spatially resolved probe measurements away from the plate reveal an EEP$f$ which asymptotes toward a Maxwellian with $T_{e}\sim $1eV near the wafer-region. Microwave opaqueness of the over-dense plasma and electron-neutral collisions contribute to the demise of the beam-component of the EEP$f$ making it a genuine decoupled plasma. [Preview Abstract] |
Tuesday, October 20, 2009 2:15PM - 2:30PM |
HT2.00004: The Presence of Normal Modes Above a Capacitive Plasma Applicator Walter Gekelman, Michael Barnes, Steven Vincena, Patrick Pribyl Normal modes of standing waves in the plasma potential have been observed over the entire surface of a dual-frequency capacitive applicator immersed in an inductively-generated rf glow discharge. An emissive probe used to measure the plasma potential is located 0.95 cm above the applicator and moved by a two-dimensional drive system. The heater current to the probe is switched off during the 100 $\mu $s measurement to eliminate uncertainties due to the heater voltage. Vp is mapped at 208 spatial locations and digitized at 1 GHz. An electrically floating probe is located 1.84 cm above the center of applicator to afford a means to generate correlation functions for the detection of waves in the low temperature plasma. The observed normal modes in potential can be expressed as summations of Bessel functions much as the vibrational modes in circular membranes and plates. The modes are most likely excited by the oscillations of the plasma-sheath interface including harmonic oscillations arising from the nonlinear mechanisms governing the sheath dynamics. As the frequency is increased, the order of the normal modes is postulated to increase as these modes are likely determined by the impedance terminating conditions on the chamber surfaces. [Preview Abstract] |
Tuesday, October 20, 2009 2:30PM - 2:45PM |
HT2.00005: Gas Temperature Measurement in a Glow Discharge Plasma Kenneth Sloneker, Nirmol Podder, William E. McCurdy, Shi Shi In this study a relatively inexpensive quartz protected thermocouple is used to measure the gas temperature in the positive column of a glow discharge plasma. For simplicity a K-type thermocouple is used to interpret the gas temperature from the sensor voltage at pressures from 0.5 Torr to 15 Torr and discharge currents from 5 mA to 120 mA. Gas temperature is investigated as a function of the gas pressure at fixed discharge currents and as a function of discharge current at fixed gas pressures in three different gas species (Ar, N$_{2}$, and He). An infinite cylinder model is used to compute the average gas temperature of the discharge from joule heating and gas thermal conductivity. The model and measurement data agree within 1{\%} to 10{\%} depending on plasma parameters. Data for all three gases have a similar quasi-linear increasing error as compared to the model. [Preview Abstract] |
Tuesday, October 20, 2009 2:45PM - 3:00PM |
HT2.00006: Ar glow discharge -- benchmark for state-of-art modeling Nicolai Dyatko, Igor Kochetov, Anatolii Napartovich, Timothy Sommerer Ar glow discharge is well studied and can serve as a reference for modeling of discharges in chemically inert gases. Paper reviews experimental works and summarizes progress in the theoretical investigation of the discharge. Special attention is focused on the new theoretical and experimental data of the elementary processes and sensitivity of the calculated plasma parameters to the uncertainty of the elementary processes and type of the chosen model. It was shown that such effects as gas rarefication and nonuniform distribution of the plasma species affect essentially on the plasma parameters and should be taken into account for correct description of discharge constriction. [Preview Abstract] |
Tuesday, October 20, 2009 3:00PM - 3:15PM |
HT2.00007: Silicon oxide permeation barrier coating of PET bottles and foils Simon Steves, Michael Deilmann, Peter Awakowicz Modern packaging materials such as polyethylene terephthalate (PET) have displaced established materials in many areas of food and beverage packaging. Plastic packing materials offer are various advantages concerning production and handling. PET bottles for instance are non-breakable and lightweight compared to glass and metal containers. However, PET offers poor barrier properties against gas permeation. Therefore, the shelf live of packaged food is reduced. Permeation of gases can be reduced by depositing transparent plasma polymerized silicon oxide ($\rm{SiO_{x}}$) barrier coatings. A microwave (2.45~GHz) driven low pressure plasma reactor is developed based on a modified Plasmaline antenna to treat PET foils or bottles. To increase the barrier properties of the coatings furthermore a RF substrate bias (13.56~MHz) is applied. The composition of the coatings is analyzed by means of Fourier transform infrared (FTIR) spectroscopy regarding carbon and hydrogen content. Influence of gas phase composition and substrate bias on chemical composition of the coatings is discussed. A strong relation between barrier properties and film composition is found: good oxygen barriers are observed as carbon content is reduced and films become quartz-like. Regarding oxygen permeation a barrier improvement factor (BIF) of 70 is achieved. [Preview Abstract] |
Tuesday, October 20, 2009 3:15PM - 3:30PM |
HT2.00008: Transverse Gas Flow RF Slab Discharge Generator of Singlet Delta Oxygen for Oxygen-Iodine Laser Andrey Ionin, Yurii Klimachev, Oleg Rulev, Leonid Seleznev, Dmitry Sinitsyn, Igor Kochetov, Anatoly Napartovich Results of experimental and theoretical study of singlet delta oxygen (SDO) production in transverse gas flow RF slab discharge for an electric discharge oxygen-iodine laser are presented. The electric discharge facility operating in both pulse-periodic and CW mode was manufactured: gas flow duct including multi-path cryogenic heat exchanger, dielectric slab channel, and slab electrode system incorporated in the channel for RF discharge ignition. Experiments on SDO production in transverse gas flow RF discharge were carried out. SDO production depending on gas mixture content, gas mixture, gas flow velocity, low-frequency modulation of RF power and RF discharge power was experimentally studied. It was shown that SDO yield increased with gas pressure decrease, gas flow deceleration and helium dilution of oxygen at the same input power. CW RF discharge was demonstrated to be the most efficient for SDO production at the same averaged input power of RF discharge. SDO yield was demonstrated to be not less than 10 percent. [Preview Abstract] |
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