Bulletin of the American Physical Society
72nd Annual Gaseous Electronics Conference
Volume 64, Number 10
Monday–Friday, October 28–November 1 2019; College Station, Texas
Session PR2: Microdischarges: Direct Current, Radiofrequency, Microwave |
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Chair: Sebastian Wilczek, Ruhr-University Bochum, Germany Room: Century II |
Thursday, October 31, 2019 10:00AM - 10:15AM |
PR2.00001: Synthesis of boron nitride using a micro hollow cathode discharge deposition reactor. Claudia Lazzaroni, Salima Kasri, Hiba Kabbara, Guillaume Lombardi, Vianney Mille, Alexandre Tallaire, Kristaq Gazeli, Joao Santos Sousa A Micro Hollow Cathode Discharge reactor in Ar/N$_{\mathrm{2}}$ gas mixtures is used to deposit hexagonal boron nitride (h-BN), a strategic material which is highly demanded for electronic and optoelectronic applications. The deposition reactor is composed of two chambers and the micro-plasmas, arranged into an array, are located at the junction between them. The plasma source consists of an anode-dielectric-cathode sandwich through which one or several holes of 400 \textmu m in diameter are drilled. The higher pressure chamber (several tens of mbar), favors the production of high density plasma, and consequently high nitrogen dissociation, while the lower pressure chamber (several mbar) limits the nitrogen recombination. The polarizable and heating substrate holder is located in the lower pressure chamber where the boron precursor (BBr$_{\mathrm{3}})$ is injected. The polarization of the substrate holder allows the discharge to be expanded from the holes to the substrate. The Ar/N$_{\mathrm{2}}$ plasma properties are characterized by optical emission spectroscopy to help the process optimization. The deposited films show a clear signature of h-BN on Raman spectra but the crystalline and surface quality still needs to be improved. The influence of the operating conditions (substrate nature and temperature, gas mixture,..) on the deposited film properties will be presented. [Preview Abstract] |
Thursday, October 31, 2019 10:15AM - 10:30AM |
PR2.00002: Study of DC and impulse discharges at sub-micrometer gap distances in various gases Nathan Ngouoto, Olivier Lesaint, Nelly Bonifaci, Olivier Gallot-Lavallee, Nawres Sridi-Convers, Christophe Poulain Using a point to plane electrode system and high precision positioning system, gap distances down to 100 nm are obtained. An hermetic enclosure allows to control the gas nature and pressure during breakdown experiments. A 1~mA current criterion is used to determine the breakdown voltage. Discharges can occur in various gases below 300 V in sub-micrometer gaps. This study enables to compare breakdown voltage under DC and impulse discharges, versus pressure and distance in various gases (dry air, N2, Ar, He). Time delay to breakdown are also obtained under fast impulse. At the shortest gaps, breakdown discharges occur at voltage lower than 100V, strongly departing from the Paschen curve. Results are discussed in terms of classical gas discharge mechanisms, modified by Fowler-Nordheim electron emission. [Preview Abstract] |
Thursday, October 31, 2019 10:30AM - 11:00AM |
PR2.00003: EEDF and plasma chemistry control in micro atmospheric pressure plasma jets by Voltage Waveform Tailoring Invited Speaker: Ihor Korolov Radio frequency excited microscopic atmospheric pressure plasmas have been receiving increasing attention in both academic and applied research. The reactive species generated in such plasma sources are important for various applications, e.g., sterilization, bacteria/cancer cell deactivation, wound healing, exhaust gas cleaning, surface treatment of different materials, and semiconductor manufacturing. Here, based on experiments and kinetic Particle-in-Cell/Monte Carlo simulations of discharges in helium with N$_{\mathrm{2}}$ admixtures, we demonstrate Voltage Waveform Tailoring to allow to control the dynamics of energetic electrons, the electron energy distribution function in distinct spatio-temporal regions of interest, and, thus, the generation of atomic nitrogen as well as helium metastables, which are highly relevant for a variety of technological and biomedical applications. By tuning the number of driving frequencies and the reactive gas admixture, the generation of these important species can be optimized and the discharge chemistry can be customized.\\ \\In Collaboration with: Zolton Donko, Peter Hartmann; Wigner Research Centre for Physics, Lena Bischoff, Gerrit Hubner; Ruhr-University, Timo Gans; University of York, Yue Liu, Thomas Mussenbrock; Brandenburg University of Technology, Julian Schulze; West Virginia University, Ruhr-University [Preview Abstract] |
Thursday, October 31, 2019 11:00AM - 11:15AM |
PR2.00004: Plasma chemistry and reactive species generation in radio-frequency micro atmospheric pressure plasma jets Y. Liu, Thomas Mussenbrock, L. Bischoff, G. Huebner, I. Korolov, J. Schulze One of the biggest advantages of radio frequency micro atmospheric pressure plasma jets ($\mu$APPJs) is the application of various reactive species to plasma surface treatments. Those reactive species are generated through complex plasma chemical reactions. In this work, based on two dimensional fluid dynamic simulations and experiments, electron heating dynamics mode transitions have been studied in helium oxygen gas mixture. More importantly, we address that mode transitions are sensitive to the electronegativity, i.e., the rate constant of the negative ion generation reaction. By comparison with experimental results, we predict a more reasonable rate constant of a 3-body attachment reaction from two databases in simulations, which is the main generation of O$_2^-$. Moreover, the control of the electron heating dynamics by using voltage waveform tailoring is demonstrated to play a significant role for the density and the distribution of reactive neutral species. [Preview Abstract] |
Thursday, October 31, 2019 11:15AM - 11:30AM |
PR2.00005: Zero-dimensional simulation of He and He/O$_{2}$ microscale atmospheric pressure plasma jet: Role of the vibrationally excited O$_{2}$ Youfan He, Anthony Etienne Ezeabasili, Efe Kemaneci Reactive oxygen species at high concentrations produced in microscale atmospheric pressure plasma jet remains at room temperature, which is particularly suitable for biomedical applications. The chemical kinetics of such species is analyzed by a developed zero-dimensional(volume-averaged) global model based on particle and electron energy balance equations. The simulation results are benchmarked against the available measurement data of He and He/O$_{2}$ plasma. The wall recombination of O plays an important role in O and O$_{3}$ concentration. The most dominant reaction for O$_{3}$ production is the three-body reaction of He, O, and O$_{2}$. The vibrational kinetics of O$_{2}$ has a negligible influence on O density, electron density, and electron temperature. [Preview Abstract] |
Thursday, October 31, 2019 11:30AM - 11:45AM |
PR2.00006: Self-consistent modeling of a linear microwave plasma source Stefan Merli, Andreas Schulz, Matthias Walker Microwave plasmas have a wide range of technical applications such as thin film deposition, etching, surface activation or gas conversion. The Duo-Plasmaline, a linearly extended low pressure microwave plasma source, is particularly suitable for such purposes because it can be extended to several meters in length and can produce large volume, high density plasmas. To better understand the processes occurring in these plasmas, a self-consistent numerical model is used to investigate the spatial and temporal evolution of hydrogen discharges. An FEM-based fluid-plasma model, which is coupled to the Maxwell's equations for the microwave field is used. A reduced set of reactions, including electron impact collisions, heavy particle reactions and wall reactions, is considered. The distribution of important plasma quantities, such as electron density and energy, as well as the densities of ionized, excited, and neutral species are studied in terms of gas pressure and microwave power. The simulation results are compared with experimental data. [Preview Abstract] |
Thursday, October 31, 2019 11:45AM - 12:00PM |
PR2.00007: Electron energy distribution function evolution in microwave microplasma Arghavan Alamatsaz, Ayyaswamy Venkattraman Microwave microplasmas have been an active research area in the last decade due to their interesting applications. Due to the challenges associated with detailed experimental study of electron dynamics in microplasmas, numerical simulations have played an important role in improving our understanding of microwave microplasmas operation. Most of these computational studies have utilized a continuum approach with only a few studies using kinetic methods. In a recent work, we compared particle-in-cell with Monte Carlo collision (PIC-MCC) method and a fluid model in the microwave regime illustrating reasonable agreement with respect to plasma number density, applied potential, and current density. In this study, the goal is to further the investigation and determine the underlying reasons for the similarities or discrepancies between the microplasma behaviors predicted by the two methods by comparing their electron energy distribution functions (EEDF). In this regard, PIC-MCC simulations are performed for argon microwave microplasmas at excitation frequencies ranging from microwave to THz and the obtained EEDF is compared with the one predicted by zero-dimensional Boltzmann solvers (such as BOLSIG$+)$ which is usually used in continuum models. The role of excitation frequency on the evolution of the EEDF and its consequences on the numerical predictions of a continuum simulation are presented. Specific emphasis is placed on the time evolution of the EEDF (during one cycle) in the vicinity of the oscillating sheath edge where a significant fraction of the heating occurs at moderate frequencies. [Preview Abstract] |
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