Bulletin of the American Physical Society
75th Annual Gaseous Electronics Conference
Volume 67, Number 9
Monday–Friday, October 3–7, 2022;
Sendai International Center, Sendai, Japan
The session times in this program are intended for Japan Standard Time zone in Tokyo, Japan (GMT+9)
Session FM2: Workshop III: Functional Surfaces in Plasma Elementary and Process-Applicable Reactions |
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Chair: Osamu Sakai, The University of Shiga Prefecture Room: Sendai International Center Shirakashi 1 |
Monday, October 3, 2022 10:30AM - 11:15AM |
FM2.00001: Application of hyperthermal spin- and alignment-controlled O2 beam to surface reaction analysis Invited Speaker: Mitsunori Kurahashi Clarification of reactivity of species contained in plasma to solid surfaces is considered necessary for understanding the plasma-surface interaction. Concerning the molecular species with kinetic energies of 10 meV -a few eV, their interaction with surfaces has been investigated intensively due to its importance in thermal gas-surface reactions. Molecular beams with well-defined kinetic energies and internal states have often been used for such purpose. O2 is involved in many technologically important processes such as heterogeneously catalyzed reactions, corrosion, and semiconductor processes. Since O2 is a linear molecule with an electron spin, the alignment of the molecular axis and/or the spin state during its collision with surfaces need to be considered for understanding the reaction mechanism. A spin-rotational state-selected O2 beam developed by us permits the experimental clarification of such effects [1]. We have recently applied this technique to the study of O2 chemisorption on flat and stepped Pt surfaces, which is technologically important as the initial step of O2 reduction reaction in fuel cell and catalytic oxidative purification of car exhaust gas. Our studies have clarified that the activation energy for O2 chemisorption depends strongly on its alignment relative to the surface; molecules with its axis nearly parallel to the surface mainly contribute the O2 chemisorption and subsequent CO oxidation reaction at kinetic energy < 0.2 eV, but O2 molecules with unfavorable alignment also react at high energy conditions. Catalytic CO oxidation reaction induced by atomic oxygen will also be presented for comparison. [1] M. Kurahashi, Prog. Surf. Sci., 91, 29 (2016). |
Monday, October 3, 2022 11:15AM - 12:00PM |
FM2.00002: Molecular Dynamics Simulations in Plasma-wave-material Interaction for Nuclear Fusion Study Invited Speaker: Hiroaki Nakamura In a fusion plasma device, the high-temperature plasma must be confined in a vacuum vessel, where the plasma is designed to contact the divertor plate to minimize vessel depletion. We used molecular dynamics (MD) to study the damage to the divertor plates caused by plasma irradiation. Here, the plasma-matter interaction (PMI) is calculated by MD for elementary processes. Recently, starting from this PMI study, we have extended the range of its application beyond the divertor plate: MD allows us to obtain the trajectory of the motion of a lot of of particles by numerical integration of the classical equations of motion. We took advantage of this feature to quantitatively evaluate the effect of tritium on biomolecules (DNA). Tritium is the fuel of fusion reactors and a radioactive isotope of hydrogen. Only the internal exposure when tritium is taken into the body needs to be controlled. For fusion power generation to be accepted by society, it is necessary to accumulate scientific knowledge so that the risk of tritium can be rigorously evaluated. Therefore, DNA damage caused by tritium was evaluated using MD. The third topic is the electromagnetic (EM) field often used in the heating of fusion plasmas. We consider optical vortices, which are EM beams with orbital angular momentum. It is known that when a metal is irradiated by an optical vortex, the surface of the material becomes a helical nanostructure, which we have succeeded in creating on the computer using MD. As mentioned above, we introduce three examples of MD research used in fusion research. |
Monday, October 3, 2022 12:00PM - 1:30PM |
FM2.00003: Lunch
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Monday, October 3, 2022 1:30PM - 2:15PM |
FM2.00004: Fibrous nanostructures formation using helium plasma and their applications as functional materials Invited Speaker: Kenzo Ibano Growth of fibrous nanostructures by helium plasma irradiation has been found on the surface of transition metals such as tungsten and molybdenum. These fibrous nanostructured surfaces are expected to be applied as functional materials because of their increased surface area and high photon absorption rates. |
Monday, October 3, 2022 2:15PM - 3:00PM |
FM2.00005: Dynamics of plasma and catalyst interfacial reactions: in situ IR spectroscopy of CO2 hydrogenation Invited Speaker: Tomohiro Nozaki The use of renewable electricity to catalyze CO2 to useful chemicals is recognized as a promising decarbonizing technology [1]. We propose nonthermal plasma combined heterogeneous catalysis as a new concept of an electricity-driven chemical reaction while utilizing renewable energy [2,3]. The catalytic surface reaction is modified by vibrationally-excited CO2, leading to smaller activation energy than that of thermal catalysis [4]. In this study, DBD (dielectric barrier discharge) combined bimetallic alloy catalyst was applied to Reverse Water Gas Shift (RWGS) reaction (CO2 + H2 = CO + H2O ΔH = 41 kJ/mol). The CO2 conversion exceeded the thermal equilibrium limit when Pd2Ga/SiO2 (10wt%) alloy catalyst was coupled with 100 kHz DBD. The in situ transmission infrared (TIR) spectroscopy was employed during DBD exposure over the alloy catalyst. The formation of monodentate formate (m-HCOO) was promoted by direct interaction between adsorbed hydrogen and vibrationally excited CO2 via the Eley-Rideal pathway. Moreover, the dissociation of m-HCOO, as a rate-determining step, was promoted clearly by DBD under hydrogen-rich conditions. Such unique reaction behavior was confirmed kinetically by the fluidized-bed DBD reactor [5], showing the activation energy of 75 kJ/mol for thermal catalysis and a drastic reduction to 44 kJ/mol for plasma catalysis. Density functional theory (DFT) calculation supports consistently in situ TIR spectroscopy and kinetic analysis of plasma catalysis of RWGS reaction. The individual role of DBD and alloy catalyst over the synergistic effect is discussed. |
Monday, October 3, 2022 3:00PM - 3:30PM |
FM2.00006: Coffee Break
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Monday, October 3, 2022 3:30PM - 4:15PM |
FM2.00007: Kinetic Simulation of Narrow Gap Discharge Invited Speaker: June Young Kim Starting from Townsend’s theory for the gas breakdown, there have been numerous studies attempting to understand the mechanism of the discharge under various conditions [1]. Especially, recent studies [2,3] proposed a universal theory for a gas breakdown from microscale to the Paschen law. They implemented equations with dimensionless variables to derive the breakdown conditions. In contrast to the model developed with simplified geometry and operating condition, the actual plasma process contains complex variables such as background plasma, complex gap geometry, plasma-solid interaction, magnetic field, and pressure gradient in the narrow gap. These variables make the model difficult to solve with analytical equations and to understand the narrow gap discharge mechanism. From the collaborative project with the kinetic simulation of Princeton Plasma Physics Laboratory, we introduce the detailed breakdown mechanism in these complex conditions and provide solutions to prevent unexpected discharge in the semiconductor-process chamber. |
Monday, October 3, 2022 4:15PM - 5:00PM |
FM2.00008: Advanced functional thin films for energy conversion and storage devices deposited by plasma-based processes Invited Speaker: Eugen Stamate Energy conversion and storage devices are essential to reach sustainability and CO2 emission reduction. Solar cells, fuel and electrolysis cells, batteries and supercapacitors are under a stringent development that requires functional materials and interfaces with tunable properties that can provide the needed device performance. The multilayered structure, involving electrodes, electrolytes, absorbers, mixed or charge dependent conductors are shrinking in size and sometimes evolve from 2D to 3D architectures. [1] Within this development, to the classic methods for materials synthesis (sintering, doctor blade, tape casting and ball milling) plasma based or assisted technologies such as sputtering, chemical vapor deposition, atomic layer deposition or thermal spray started to contribute as well. In this context, this work provides an overview on current and potential use of plasma technologies for functional thin films for energy conversion and storge device with focus on solar cells, fuel cells and micro batteries. Special attention is dedicated to metal oxides by magnetron sputtering where the role of energetic oxygen-negative-ions is corelated with plasma and thin film properties as well as with the growth mechanism. A dual thermal-electrostatic probe used to measure plasma density, electron temperature and plasma potential, revealed that the best conditions to deposit metal oxides, under growth assistance of low-energy oxygen negative ions, corresponds to the transition from a plume-like discharge to magnetron. Analytical characterization using TOF-SIMS and 2D-XRD demonstrated that preferential sputtering can play a significant role for binary metal oxides with significant differences in sputtering yield as for aluminum doped zinc oxide. [3] |
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