Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session FT3: MicroplasmasFocus
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Chair: D.Z. Pai, CNRS, Universite de Poitiers Room: 2b |
Tuesday, October 11, 2016 2:00PM - 2:30PM |
FT3.00001: Operating principles of microplasmas assisted by field emitting cathodes Invited Speaker: Ayyaswamy Venkattraman Microplasmas have contributed to an exciting new direction in low-temperature plasma science and engineering with various applications including electronics, nanomaterial synthesis, and lighting to name a few. The rapid miniaturization of microplasma devices has provided the opportunity to exploit physical mechanisms that are considered unimportant in traditional macroscale plasmas. Specifically, the intense electric fields encountered in microplasma devices lead to an auxiliary source of electrons via field-induced electron emission from the electrodes. Also, recent advances in nano/microfabrication have resulted in the engineering of thin film materials (such as ultrananocrystalline diamond) with field emission threshold electric fields as low as 1 $V/\mu m$ thereby allowing us to exploit them in microplasmas with dimensions $\sim$ 100 $\mu m$. In this regard, this talk deals with the principles that govern the operation of microplasma devices assisted by field emitting cathodes. Specifically, the talk will focus on the interesting interplay between field emission and the corresponding microplasma properties with surface-normal electric field serving as the link. Results are presented for the operating modes of field emission assisted microplasmas in the direct current and radio frequency/microwave regimes. The one-dimensional analyses include a combination of simplified global/spatial sheath models, fluid simulations as well as kinetic simulations using the particle-in-cell with Monte Carlo collisions (PIC-MCC) method. Two-dimensional fluid simulations are also presented for microcavity plasmas augmented by field emitting cathodes. The simulations are validated with experimental data whenever possible and a need for additional suitable experimental datasets is highlighted. [Preview Abstract] |
Tuesday, October 11, 2016 2:30PM - 2:45PM |
FT3.00002: Low temperature, high-density microplasma plume generated in a micro-tube with variable inner diameter Jianmin Gou, Xinpei Lu A low temperature helium microplasma plume generated in a micro quartz tube with inner diameter decreasing from 245 $\mu $m to 6 $\mu $m is reported. The microplasma plume has a length of around 1.5 cm and reaches the position with its diameter down to 10 $\mu $m. Though the inner diameter of the tube is in sub-millimeter, the cross section of the tube is not fully filled with the plasma only until the tube inner diameter is down to 30 $\mu $m. The electron density estimated from H$_{\mathrm{\alpha }}$ stark broadening increases as the inner diameter of the tube decreases. The ignition voltage increases from 11 kV to 40 kV as the diameter of the inner quartz tube decreases from 245 $\mu $m to 10 $\mu $m. Further analysis shows that, in order to ignite a non-equilibrium plasma plume in 1 $\mu $m diameter tube, the applied voltage of about 65 kV is needed and the plasma density could reach as high as on the order of 10$^{\mathrm{18}}$ cm$^{\mathrm{-3}}$, which is interesting for the studies of several fundamental phenomena such as plasma sheath structure. [Preview Abstract] |
Tuesday, October 11, 2016 2:45PM - 3:00PM |
FT3.00003: Enhanced lifetime for thin-dielectric microdischarge-arrays operating in DC Remi Dussart, Valentin Felix, Lawrence Overzet, Olivier Aubry, Arnaud Stolz, Philippe Lefaucheux Micro-hollow cathode discharge arrays using silicon as the cathode have a very limited lifetime because the silicon bubbles and initiates micro-arcing [1]. To avoid this destructive behavior, the same configuration was kept but, another material was selected for the cathode. Using micro and nanotechnologies ordinarily used in microelectronic and MEMS device fabrication, we made arrays of cathode boundary layer (CBL)-type microreactors consisting of nickel electrodes separated by a 6 \textmu m thick SiO$_{\mathrm{2}}$ layer. Microdischarges were ignited in arrays of \textasciitilde 100 \textmu m diameter holes at different pressures (200{\-}750 Torr) in different gases. Electrical and optical measurements were made to characterize the arrays. Unlike the microdischarges produced using silicon cathodes, the Ni cathode discharges remain very stable with essentially no micro-arcing. DC currents between 50 and 900 \textmu A flowed through each microreactor with a discharge voltage of typically 200 V. Stable V-I characteristics showing both the normal and abnormal regimes were observed and are consistent with the spread of the plasma over the cathode area. Due to their stability and lifetime, new applications of these DC, CBL-type microreactors can now be envisaged. [1] V. Felix \textit{et Al.} Plasma Sources Sci. Technol., 25, 025021(2016) [Preview Abstract] |
Tuesday, October 11, 2016 3:00PM - 3:15PM |
FT3.00004: Global model of a micro hollow cathode discharge in Ar /N$_{\mathrm{2}}$ used for nitride synthesis Claudia Lazzaroni, Salima Kasri A global model of a Micro Hollow Cathode Discharge (MHCD) in argon (Ar) with an admixture of nitrogen (N$_{\mathrm{2}})$, working at several hundreds of Torr, is presented. MHCDs allow high electron densities and therefore high dissociation degree of nitrogen to be reached which is particularly suited for nitride deposition given the high bond energy of molecular nitrogen. The global model is based on the numerical resolution of the particle balance equations and the power balance equation. The model is run until the steady state is reached and we obtain the plasma parameters that are the species densities and the electron temperature. A particular focus is given to the atomic nitrogen density, a key parameter for the deposition and growth of nitride films. A parametric study is done varying the gas pressure and the N$_{\mathrm{2}}$ fraction in Ar. Despite being fed by a DC power supply, MHCDs operate in steady state and in self-pulsed mode, both captured by the model. The effect of the MHCD mode (steady or self-pulsed) on the plasma parameters is also presented. [Preview Abstract] |
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