Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session ET2: Microdischarges |
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Chair: Osamu Sakai, Kyoto University Room: 151 |
Tuesday, October 5, 2010 4:00PM - 4:15PM |
ET2.00001: Model of the dynamics of the self-pulsing regime in a micro hollow cathode discharge in argon Claudia Lazzaroni, Pascal Chabert, Antoine Rousseau Under certain conditions, a micro hollow cathode discharge (MHCD) presents a self-pulsing regime despite a continuous power supply, where the discharge current and the discharge voltage oscillate with a frequency of several tens of kHz. Based on the works of Hsu \textit{et al.} (2003) and Aubert \textit{et al.} (2006), an equivalent circuit model is proposed to understand the physics of these oscillations. A model of the non-linear resistance is proposed and the dynamics is analyzed. The model reproduces the electrical signals observed experimentally. The discharge current obtained thanks to this electrical model is used as an input parameter of a zero dimensional unstationnary model of the argon plasma. This global model combines the particle and the energy balance equations. The temporal evolution of the species densities (electrons, atomic and molecular ions, metastables) and of the electron temperature are obtained during the cycles of the self-pulsing. The electron density, which can reach a maximum of 10$^{16}$ cm$^{-3}$ at 150 Torr, follows the temporal evolution of the discharge current with slightly longer characteristic rise and decay times. [Preview Abstract] |
Tuesday, October 5, 2010 4:15PM - 4:30PM |
ET2.00002: Micro Hollow Cathode Discharge Arrays in silicon devices Remi Dussart, Mukesh Kulsreshath, Lawrence Overzet, Laurent Schwaederle, Thomas Tillocher, Julien Ladroue, Olivier Aubry, Philippe Lefaucheux, Matthew Goeckner, Pierre Ranson Micro-hollow cathode discharge (MHCD) arrays are of interest for many applications including plasma processing at atmospheric pressure. Silicon was the selected material to form the reactors because it is convenient for microfabrication and it offers good mechanical and thermal properties. Our objective is to fabricate and study MHCD arrays in DC to investigate their limits and characteristics for their potential applications. We fabricated cathode boundary layer (CBL)-type reactors consisting of a silicon cathode separated from a Nickel anode by an SiO$_{2}$ layer. Different geometries of cathode were investigated. Arrays containing up to 1024 holes of different diameter (25-150 $\mu $m) were ignited at different pressures (100--1000 Torr) in He and Ar. Imaging, electrical and spectroscopic measurements were carried out to characterize the arrays. Paschen curves have been plotted to study the breakdown mechanisms. We will present results to ignite microdischarges of the whole array versus pressure and current. [Preview Abstract] |
Tuesday, October 5, 2010 4:30PM - 4:45PM |
ET2.00003: Breakdown Phase of Pulsed N$_{2}$/He Atmospheric-pressure Micro-hollow Cathode Discharge Plasma Toshiki Nakano, Shinya Wake, Takeshi Kitajima The breakdown phase of a pulsed N$_{2}$/He atmospheric-pressure micro-hollow cathode discharge plasma is studied by temporally resolved N$_{2}$ optical emission spectra as well as the waveforms of discharge current and voltage. The simultaneous measurements of N$_{2}$ emission and current in the pulsed plasma reveal the appearance of the current pulses which coincide with N$_{2}$ emission in the breakdown phase. N$_{2}$ emission intensity exhibits a sharp peak in the breakdown phase and becomes constant in the glow-discharge phase. Temporal variation of N$_{2}$ emission spectra indicates that N$_{2}$ rotational temperature remains below 500 K immediately after discharge ignition but rises promptly to 1000 K within 20 $\mu $s after the ignition. The average N$_{2}$ emission intensity during a current pulse in the breakdown phase is 3 orders of magnitude higher than that in the glow-discharge phase whereas the energy required for N$_{2}$ emission is lower by a factor of 60 during the current pulse than in the glow-discharge phase. Thus, in the breakdown phase, the plasma with high excitation and dissociation rates is likely to be generated efficiently even though neutral temperature remains low. [Preview Abstract] |
Tuesday, October 5, 2010 4:45PM - 5:00PM |
ET2.00004: VUV light source based on Cl-atom emission produced by a microdischarge Virginie Martin, Gerard Bauville, Vincent Puech Cl2 based plasmas are widely used to etch silicon in semiconductor manufacturing. The etching rates are dependent on the Cl-atom flux impacting onto the surface, so that the measurement of the Cl atom density is of prime importance. However accurate measurements of Cl atom density in the plasma is still a challenge and only rough estimates are usually indirectly obtained. We developed a VUV light source emitting on the resonance lines of Cl atom which could be implemented on any etching reactor to perform direct measurements of the Cl atom density through absorption spectroscopy. The light source is mainly composed of a micro hollow cathode discharge (MHCD) operating in an Ar/Cl2 mixture. The diameter of the MHCD hole is lower than 1mm resulting in a high current density discharge with a high density of excited Cl atoms. While the discharge spreads on the back side of the cathode, it remains confined inside the hole on the anode side, in such a way that the plasma appears as a point-like source which can be easily coupled with the entrance slit of a VUV monochromator. In the range 130-140nm, the evolution of the emission intensity of the Cl lines have been studied versus the partial and total pressures and the discharge current. The best discharge conditions allowing achieving simultaneously good spectral resolution, high emission intensity and long term stability will be reported. [Preview Abstract] |
Tuesday, October 5, 2010 5:00PM - 5:15PM |
ET2.00005: Scaling microplasma arrays for material processing Chen Wu, Naoto Miura, Jun Xue, Michael Grunde, Kevin Morrissey, Jeffrey Hopwood Microwave-generated microplasma produces a dense, continuous discharge because the period of the electric field is shorter than the electron confinement time. The electrons are trapped in the plasma between two resonating microelectrodes driven at $\sim $1 GHz. Stark broadening of the atomic hydrogen emission shows the time-average electron density is $\sim $10$^{14}$ cm$^{-3}$ at atmospheric pressure in argon at 1 watt of absorbed power. Gas temperature remains less than 900 K according to laser diode absorption profiles of the Ar metastable states. These conditions suggest that microplasmas can provide a high ion flux to a surface while maintaining low surface temperatures. In an effort to scale the microplasma to lengths that are compatible with roll coating, we present coupled arrays of resonator-driven microplasma. Hundreds of microplasmas can be sustained in parallel using a single microwave power source. Coupled mode theory provides the physical description of these line-shaped cold atmospheric plasmas. Stability of the microplasma is due to detuning of each resonator by the plasma sheath capacitance and plasma resistance. Examples of hydrocarbon deposition will be discussed. [Preview Abstract] |
Tuesday, October 5, 2010 5:15PM - 5:30PM |
ET2.00006: MIP source for analytical applications: experimental and simulation study Margarita Baeva, Andre B\"{o}sel, J\"{o}rg Ehlbeck, Detlef Loffhagen Experimental and simulation studies of a waveguide-based microwave induced plasma (MIP) source which operating at 2.45 GHz in atmospheric pressure helium gas are presented. The plasma source is aimed at optical emission spectroscopy and has a small discharge volume, low gas flow and microwave power at high power density to obtain high excitation temperatures. The emitted spectra have been observed for various gas flow and microwave power values. the rotation and excitation temperatures derived from the spectra are found to be between 2000 K and 4000 K. The measurements are completed by a collisional radiative (CR) model delivering the electron density and temperature, amplitude of the electric microwave field, and population of the excited atomic states for a given absorbed power and gas temperature. A two-dimensional model of the plasma source based on Maxwell's equations is further applied to obtain the distribution of the electric field and the absorbed microwave power density . The basic relations are solved for plasma density of $4.4\times10^{19}m^{-3}$ resulting from the CR model. With a total power of 40 W, an average electric field of $3.8\times10^{5} $V/m is reached. [Preview Abstract] |
Tuesday, October 5, 2010 5:30PM - 5:45PM |
ET2.00007: Microwave micro-discharges at atmospheric pressure: experiments and simulations J. Greg\'orio, O. Leroy, P. Leprince, C. Boisse-Laporte, L.L. Alves We present a microwave (2.45 GHz) source based on a planar transmission line configuration, which uses a continuous excitation (1-50 W) to produce stable micro-plasmas at atmospheric pressure in air, Ar and He (plasmas are produced within the 50-200 $\mu $m gap created between two metal electrodes). The source is studied using both experiments [1] and simulations [2]. Experiments (i) measure the return loss of the source (hence its quality factor); (ii) use OES diagnostics to obtain the plasma (ro-vibrational and excitation) temperatures and the electron density; and (iii) check the plasma expansion by resorting to an imagery analysis. Simulations (i) describe the electromagnetic behavior of the source using the numerical code CST {\textregistered} and an analytical transmission line model; and (ii) characterize the plasmas produced, using a 1D self-consistent stationary hybrid code for Ar, that solves the fluid-type transport equations coupled with the kinetic electron Boltzmann equation. The system exhibit power densities of 1-5 kW cm$^{-3}$ for electron densities of $\sim $10$^{13}$-10$^{14 }$cm$^{-3}$. [1] J. Greg\'{o}rio et al, these proceedings; [2] L.L. Alves et al, these proceedings. [Preview Abstract] |
Tuesday, October 5, 2010 5:45PM - 6:00PM |
ET2.00008: Conversion of Organic Compounds by Pulsed Discharge Plasma in Sub- and Supercritical Fluids Motonobu Goto, Mitsuru Sasaki, Diono Wahyu, Koichi Nagafuchi, Hiroshi Watanabe, Tsuyoshi Kiyan, Takao Namihira, Hidenori Akiyama Discharge plasmas in sub- and supercritical fluids have high possibilities as a novel reaction field. We have studied generation of pulsed discharge plasma in subcritical or supercritical fluids, such as carbon dioxide, water, or argon. Two-phase system, where liquid and supercritical fluid coexist, was also used as a media to generate discharge plasma. The discharge behavior was investigated in terms of breakdown phenomena. Plasma generated in supercritical carbon dioxide was used for the reaction of palmitic acid. By treating at 313 K, 15 MPa, and 2000 times plasma discharges, production of myristic acid and stearic acid was observed, indicating C-C bond cleavage or C-C bond formation. We also applied plasma generated in subcritical water to chemical reactions of phenol and aniline. Phenol was decomposed to 17{\%} of the conversion after 4,000 times discharged at 523 K, 25 MPa. The analysis of oily product found that phenol was converted into its dimer and trimer. In trimer, hydroxyl radical of phenoxy radical was bonded at meta position in phenol. When aniline was used as a reactant, the polymerization of aniline was also observed. [Preview Abstract] |
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