Propagation of Plasma Diffusion Wave According to the Voltage Polarity in the Atmospheric Pressure Plasma Jet Columns

Guangsup Cho,Yun-Jung Kim,Eun Ha Choi,Han Sup Uhm IEEE 2014 IEEE transactions on plasma science Vol.42 No.11

<P>Propagation of optical signals measured along the atmospheric plasma-jet column according to the operational voltage polarity is analyzed with the electrostatic plasma-diffusion wave in terms of the characteristic speeds of plasma fluids, such as the plasma drift u<SUB>d</SUB>, the gas flow u<SUB>b</SUB>, and the plasma diffusion u<SUB>n</SUB>. For the positive voltage, the ion wave propagates with the wave-packet velocity of u<SUB>g</SUB> ~ c<SUB>s</SUB><SUP>2</SUP>/u<SUB>n</SUB>, where c<SUB>s</SUB> is the acoustic velocity along the whole column of plasma jet without any restrictions. The electron wave propagates backward with the group velocity of electron drift with u<SUB>g</SUB> ~ -u<SUB>ed</SUB> toward the high voltage electrode right after passing of the frontline of ion wave-packet. For the negative voltage, the ion wave propagates on the high ionization column with the wave-packet velocity of u<SUB>g</SUB> ~ c<SUB>s</SUB><SUP>2</SUP>/u<SUB>n</SUB>. The electron wave propagates forward while its propagation mode varies from the group velocity of u<SUB>g</SUB> ~ c<SUB>s</SUB><SUP>2</SUP>/u<SUB>n</SUB> on a region of high electric field to the velocity of electron drift with ug ~ +u<SUB>ed</SUB> on a low field region.</P>

Simulations of fusion edge plasmas by linear plasma devices: physics and plasma–material interactions

Kang In Je,Bae Min-Keun,박인선,Woo Hyun-Jong,Lho Taihyeop,Ahn Jeong-Sun,Chang Doo-Hee,조순국,Choi Geun-Sik,Choi Heung-Gyun,Choi Yong-Sup,Chung Bo-Hyun,Chung Tae Hun,Do Jeong-Joon,Goo Bon-Cheol,Hong Sunghoon 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.8

Because a fusion edge plasma contains various atomic and molecular processes, along with various plasma–material interactions (PMIs) for post-mortem analyses, a linear plasma device can simulate divertor and scrape-off layer (SOL) plasmas with DC edge relevant parameters, although it cannot generate a high ion temperature and toroidicity with much less power density compared to toroidal devices. The Divertor Plasma Simulator-2 (DiPS-2), a linear device with an LaB6 DC cathode, has been used for a few fusion-relevant physics experiments, including edge localized mode (ELM) simulation and edge transport of diffusion and convection. An ELM simulation has been performed by modulating the magnetic field relevant to the pressure modulation of a toroidal device, and the diffusion coefficients of free and bound presheaths have been measured in simulations of divertor or limiter transport. Moreover, the convection of the filament or the bubble expansion to the first wall has also been analyzed. In addition to various atomic and molecular processes in SOL and divertor plasmas, PMIs must be analyzed both on and beneath the surface of the plasma-facing components (PFCs) because of surface modification. Using DiPS-2 and other linear devices along with Korea Superconducting Tokamak Advanced Research (KSTAR), PMIs have been analyzed in terms of the following elements or processes: (1) boronizations, both for dust interactions with the surface chamber (DiSC) and KSTAR device, are analyzed; (2) carbon damage by the dense heat flux of DiPS-2 is experimentally investigated; (3) the density profile of the lithium injection gettering of hydrogen and its transport experiments (LIGHT-1) device is analytically calculated; (4) the effect of nitrogen on the relaxation of the heat flux to the divertor tile is experimentally analyzed; and (5) tungsten as the divertor tile material is analyzed via laser ELM simulations in terms of dust generation and surface modification.

EFFECT OF THE PLASMA JET IGNITION AND FLAME KERNEL UNDER THE COMBUSTION PROCESS IN A CONSTANT VOLUME COMBUSTION CHAMBER

최문석,이경태,김권세,최두석 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.4

This work is to study the plasma application using a capacitive discharge ignition capable of using the plasma jet which belongs to the non-thermal plasma physic. A plasma-jet spark plug was designed to combine a discharge chamber including an insulator and expanding the plasma area. The nonresistance was applied to acting the interference suppression of a plasma-jet spark plug to ensure the high energy generated at a DC-DC converter. An ANSYS FLUENT program was used to conduct analyzing combustion progress. The combustion simulation model is composed of configurations of a spark plug, a lambda sensor, and an internal combustion chamber. Resultantly, the minimum value of the combustion pressure is verified at λ = 1.6, and the plasma jet has higher values in the order of 2, 3, and 4 bar than the conventional models due to having a fast reaction. Consequently, the plasma jet has advantageous in combustion diffusivity in comparison to the conventional spark plug since the negative electrode of the cathode is not designed in front of a jet plug.

확산펌프 기반의 BCl₃ 축전결합 플라즈마를 이용한 GaAs와 AlGaAs의 건식 식각

이제원,이성현,박주홍,최경훈,송한정,조관식 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.4

We report the etch characteristics of GaAs and AlGaAs in the diffusion pump-based capacitively coupled BCl3 plasma. Process variables were chamber pressure (50~180 mTorr), CCP power (50~200 W) and BCl3 gas flow rate (2.5~10 sccm). Surface profilometry was used for etch rate and surface roughness measurement after etching. Scanning electron microscopy was used to analyze the etched sidewall and surface morphology. Optical emission spectroscopy was used in order to characterize the emission peaks of the BCl₃ plasma during etching. We have achieved 0.25 µm/min of GaAs etch rate with only 5 sccm BCl₃ flow rate when the chamber pressure was in the range of 50~130 mTorr. The etch rates of AlGaAs were a little lower than those of GaAs at the conditions. However, the etch rates of GaAs and AlGaAs decreased significantly when the chamber pressure increased to 180 mTorr. GaAs and AlGaAs were not etched with 50 W CCP power. With 100~200 W CCP power, etch rates of the materials increased over 0.3 µm/min. It was found that the etch rates of GaAs and AlGaAs were not always proportional to the increase of CCP power. We also found the interesting result that AlGaAs did not etched at 2.5 sccm BCl3 flow rate at 75 mTorr and 100 W CCP power even though it was etched fast like GaAs with more BCl3 gas flow rates. By contrast, GaAs was etched at ~0.3 µm/min at the 2.5 sccm BCl3 flow rate condition. A broad molecular peak was noticed in the range of 500~700 nm wavelength during the BCl₃ plasma etching. SEM photos showed that 10 sccm BCl₃ plama produced more undercutting on GaAs sidewall than 5 sccm BCl₃ plasma. 본 논문은 확산펌프 기반의 축전 결합형 BCl3 플라즈마를 사용하여 GaAs와 AlGaAs를 건식 식각한 연구에 관한 것이다. 실험에서 사용한 압력 범위는 50~180 mTorr, CCP 파워는 50~200 W, BCl₃ 가스 유량은 2.5~10 sccm 이었다. 식각 후에 GaAs와 AlGaAs의 식각 속도와 표면 거칠기분석은 표면 단차 측정기를 이용하여 하였다. GaAs의 식각 벽면과 표면 상태는 전자 현미경으로 분석하였다. 식각 중 플라즈마의 광 특성 분석은 광학 발광 분석기를 이용하였다. 본 실험을 통하여 5 sccm의 소량의 BCl3₃가스 유량으로 공정 압력이 130 mTorr이내인 경우에는, 100 W CCP 파워의 조건에서 GaAs는 약 0.25 µm/min 이상의 우수한 식각 속도를 얻을 수 있었다. AlGaAs의 경우는 GaAs의 식각 속도보다 조금 낮았다. 그러나 같은 유량에서 공정 압력이 180 mTorr로 높아지면 GaAs와 AlGaAs의 식각 속도가 급격히 감소하여 거의 식각되지 않는 것을 알 수 있었다. 또한 CCP 파워의 경우에는 50 W의 파워에서는 GaAs와 AlGaAs 모두 거의 식각되지 않았다. 그러나 100~200 W의 조건에서는 0.3 µm/min 이상의 높은 식각 속도를 주었다. 두 결과를 보았을 때 축전결합형 BCl₃ 플라즈마 식각에서 GaAs와 AlGaAs의 식각 속도는 CCP 파워가 100~200 W 범위에 있으면 그 값에 비례하지 않고 거의 일정한 값이 된다는 사실을 알았다. 75 mTorr, 100 W의 CCP 파워 조건에서 BCl₃의 유량 변화에 따른 GaAs와 AlGaAs의 식각 속도의 경우, BCl₃의 유량이 2.5 sccm의 소량일 때는 GaAs는 식각 속도가 높았지만 AlGaAs는 거의 식각되지 않는 흥미로운 결과를 얻었다. 플라즈마 발광 특성을 보면 BCl₃ 축전 결합 플라즈마는 주로 500~700 nm 범위를 가지는 넓은 분자 피크만 만든다는 것을 알 수 있었다. 전자 현미경 사진 결과에서는 5 sccm과 10 sccm의 BCl₃ 플라즈마 모두 식각 중에 GaAs의 벽면을 언더컷팅 하였으며, 10 sccm의 BCl₃ 유량을 사용하였을 때 언더컷팅이 더 심했다.

Analytic treatment of distributions of lithium neutrals and ions in linear devices

Chung, K.S.,Hirooka, Y.,Ashikawa, N.,Cho, S.G.,Choi, H.G.,Kang, I.J.,Tsuchiya, H. North-Holland 2017 Fusion engineering and design Vol.119 No.-

<P>Neutral lithium (Li) has been used for the mitigation of heat flux to the plasma facing components and for the control of hydrogen of fusion plasmas. Radial and axial variations of densities of Li neutrals and ions are obtained analytically for a cylindrical chamber by assuming the classical diffusion with or without the magnetic field (B). Neutrals and ions without B can be expressed as a linear combination of the modified Bessel functions of order zero (I-0 and K-0), while ions with B are to be expressed as the square root of them. Analytical solutions of Li neutral densities with Dirichlet and Neumann boundary conditions are compared to those using Monte Carlo simulation and experimental values of the LIGHT-1 (Lithium Injection Gettering of Hydrogen and its Transport experiments) device. Proper combinations of the relaxation length and size of the source would produce well fitted profiles similar to those observed experimentally and those using Monte Carlo codes. (C) 2017 Elsevier B.V. All rights reserved.</P>

Growth of tantalum nitride film as a Cu diffusion barrier by plasma-enhanced atomic layer deposition from bis((2-(dimethylamino)ethyl)(methyl)amido)methyl(tert-butylimido)tantalum complex

Han, J.H.,Kim, H.Y.,Lee, S.C.,Kim, D.H.,Park, B.K.,Park, J.S.,Jeon, D.J.,Chung, T.M.,Kim, C.G. New York] ; North-Holland 2016 APPLIED SURFACE SCIENCE - Vol.362 No.-

A new bis((2-(dimethylamino)ethyl)(methyl)amido)methyl(tert-butylimido)tantalum complex was synthesized for plasma-enhanced atomic layer deposition (PEALD) of tantalum nitride (TaN) film. Using the synthesized Ta compound, PEALD of TaN was conducted at growth temperatures of 150-250<SUP>o</SUP>C in combination with NH<SUB>3</SUB> plasma. The TaN PEALD showed a saturated growth rate of 0.062nm/cycle and a high film density of 9.1-10.3g/cm<SUP>3</SUP> at 200-250<SUP>o</SUP>C. Auger depth profiling revealed that the deposited TaN film contained low carbon and oxygen impurity levels of approximately 3-4%. N-rich amorphous TaN films were grown at all growth temperatures and showed highly resistive characteristic. The Cu barrier performance of the TaN film was evaluated by annealing of Cu/TaN (0-6nm)/Si stacks at 400-800<SUP>o</SUP>C, and excellent Cu diffusion barrier properties were observed even with ultrathin 2nm-thick TaN film.

Production of iron nanotubes in plasma

Ioan Bica 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.2

The paper presents the experimental installation, the procedure of obtainment and some mechanisms of iron nanotubes formation in plasma. The inner and outer diameters of nanotubes produced in this manner are located within regions like 0.1–0.45 nm and 2.2–14 nm, respectively. The length takes values between 5 and 12 nm.We emphasize that a quantized description of diameters formation is conceivable. To this aim a diameter quantum like diq~1.2 nm can be proposed. The experimental results obtained are discussed.

플라즈마 풍동의 중심체(Center-Body)형 디퓨저 유동해석 및 성능평가

백진솔(Jinsol Baek),최대산(Daesan Choi),김규홍(Kyu-Hong Kim) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.3

In this study, the flow analysis of center-body type diffuser was performed using the “ARCFLO4” flow analysis solver and, the performance of the diffuser according to various shapes and positions of the center-body was evaluated. Thermal equilibrium air was assumed and turbulence was considered. The performance of the diffuser was evaluated by using the pressure recovery rate of the diffuser, the velocity and the temperature at the diffuser outlet, which can determine the requirements of the heat exchanger and vacuum pump located behind the diffuser. As a result of the flow analysis, when the center-body is located in the whole diffuser area, the loss of total pressure due to the inclined shock wave generated in the hypersonic region was significant. Therefore, the diffuser which is center-body located in hypersonic region had disadvantages in the pressure recovery aspect. However, since the center-body type diffuser has advantages in cooling compressed high-temperature flow by increasing the cooling wall area inside the diffuser, a center-body diffuser located in subsonic region was proposed in this study. This new center-body type diffuser was able to cool flow while minimizing the total pressure loss due to shock waves.

Investigation of laterally single-diffused metal oxide semiconductor (LSMOS) field effect transistor

Avikal Bansal,M. Jagadesh Kumar 한국물리학회 2015 Current Applied Physics Vol.15 No.10

We propose a distinct approach to implement a laterally single diffused metal-oxide-semiconductor (LSMOS) FET with only one impurity doped p-n junction. In the LSMOS, a single p-n junction is first created using lateral dopant diffusion. The channel is formed in the p region of the p-n junction and the n region acts as the drift region. Two distinct metals of different work function are used to form the “n+ ” source/drain regions and “p+ ” body contact using the charge plasma concept. We demonstrate that the LSMOS is similar in performance to a laterally double diffused metal-oxide-semiconductor (LDMOS) although it has only one impurity doped p-n junction. The LSMOS exhibits a breakdown voltage of ~50.0 V, an average ON-resistance of 48.7 mΩ-mm2 and a peak transconductance of 53.6 μS/μm similar to that of a comparable LDMOS.

플라즈마 풍동 디퓨저의 형상에 따른 압력회복 성능 변화

최대산,백진솔,김규홍 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.4

Plasma wind tunnel is one of the devices that simulates hypersonic, high enthalpy environments on the ground. The diffuser, which is one of the components of the plasma wind tunnel, captures the flow ejected from the nozzle and compresses the flow, thereby enabling stable and economical test. In this study, numerical analysis was performed on the flow inside the diffuser to understand the nature of the flow and pressure recovery performance with different diffuser shape. Inflow conditions were Mach 7, 2 kg/s of mass flow rate, 530 Pa of static pressure, and 240 K of static temperature, which is based on the conditions of MW-class large capacity plasma wind tunnel. In the flow inside of a diffuser, strong shock resulted in severe total pressure loss and the pressure ratio required to operate wind tunnel. In order to investigate the influence of the change in diffuser shape, pressure recovery performances of each diffuser were compared varying diffuser converging section, throat area, and diverging section. In diffuser converging section, the pressure recovery performance was improved as the intensity of the oblique shock decreased. For the diffuser throat, the smaller the throat area, the more improved the pressure recovery. The change of the diffuser pressure recovery performance with the shape change of diverging section was relatively small. These comparative analysis could be useful for design of a diffuser for plasma wind tunnel.