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Effect of a negative DC bias on a capacitively coupled Ar plasma operated at different radiofrequency voltages and gas pressures

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Plasma Science and Technology 2024年第5期26卷 62-71页

作者：相垚君王晓坤刘永新王友年 Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024People’s Republic of China Chair of Applied Electrodynamics and Plasma Technology Ruhr University BochumBochum 44801Germany

The effect of a negative DC bias,|V_(dc)|,on the electrical parameters and discharge mode is investigated experimentally in a radiofrequency(RF)capacitively coupled Ar plasma operated at different RF voltage amplitudes and gas *** electron density is measured using a hairpin probe and the spatio-temporal distribution of the electron-impact excitation rate is determined by phase-resolved optical emission *** electrical parameters are obtained based on the waveforms of the electrode voltage and plasma current measured by a voltage probe and a current *** was found that at a low|V_(dc)|,***α-mode,the electron density and RF current decline with increasing|V_(dc)|;meanwhile,the plasma impedance becomes more capacitive due to a widened ***,RF power deposition is ***|V_(dc)|exceeds a certain value,the plasma changes toα–γhybrid mode(or the discharge becomes dominated by theγ-mode),manifesting a drastically growing electron density and a moderately increasing RF ***,the plasma impedance becomes more resistive,so RF power deposition is enhanced with|V_(dc)|.We also found that the electrical parameters show similar dependence on|V_(dc)|at different RF voltages,andα–γmode transition occurs at a lower|V_(dc)|at a higher RF *** increasing the pressure,plasma impedance becomes more resistive,so RF power deposition and electron density are *** particular,theα–γmode transition tends to occur at a lower|V_(dc)|with increase in pressure.

关键词： RF capacitively coupled plasma DC-overlapped RF discharge power deposition discharge mode transition

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Customized modulation on plasma uniformity by non-uniform magnetic field in capacitively coupled plasma

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Plasma Science and Technology 2024年第6期26卷 79-87页

作者：王森张权治马方方 Maksudbek YUSUPOV 王友年 School of Physics Dalian University of TechnologyDalian 116024People’s Republic of China Laboratory of Thermal Physics of Multiphase Systems Arifov Institute of Ion-Plasma and Laser TechnologiesAcademy of Sciences of UzbekistanTashkent 100125Uzbekistan Department of Power Supply and Renewable Energy Sources National Research University TIIAMETashkent 100000Uzbekistan

A two-dimensional fluid model based on COMSOL Multiphysics is developed to investigate the modulation of static magnetic field on plasma homogeneity in a capacitively coupled plasma(CCP)chamber. To generate a static magnetic field, direct current is applied to a circular coil located at the top of the chamber. By adjusting the magnetic field's configuration, which is done by altering the coil current and position, both the plasma uniformity and density can be significantly modulated. In the absence of the magnetic field, the plasma density exhibits an inhomogeneous distribution characterized by higher values at the plasma edge and lower values at the center. The introduction of a magnetic field generated by coils results in a significant increase in electron density near the coils. Furthermore, an increase in the sets of coils improves the uniformity of the plasma. By flexibly adjusting the positions of the coils and the applied current,a substantial enhancement in overall uniformity can be achieved. These findings demonstrate the feasibility of using this method for achieving uniform plasma densities in industrial applications.

关键词： COMSOL capacitively coupled plasma plasma uniformity magnetic field

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克里雅河流域平原区土地利用类型时空演化规律及驱动因素分析

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水利规划与设计 2024年第5期 84-89,120页

作者：王友年新疆水利水电勘测设计研究院有限责任公司新疆乌鲁木齐830000

为推动克里雅河流域土地资源的合理开发利用及绿洲湿地保护,在基于研究区30年土地覆被类型数据的基础上,分析区域土地利用类型的时空演化规律及影响因素。结果表明:近年来研究区耕地及建设用地呈增加趋势,林草地呈先减后增趋势,水域及... 详细信息

为推动克里雅河流域土地资源的合理开发利用及绿洲湿地保护,在基于研究区30年土地覆被类型数据的基础上,分析区域土地利用类型的时空演化规律及影响因素。结果表明:近年来研究区耕地及建设用地呈增加趋势,林草地呈先减后增趋势,水域及未利用地呈减少趋势;各类型土地转变频繁,其中草地和未利用地面积转变最多,建设用地转变最少;2000年后区域生态环境有所改善,荒漠化进程变缓;流域各土地利用类型的转变均主要受区域经济社会发展及人口变化的影响。克里雅河流域在今后应持续加强生态保护与修复,提高用水效率,以期实现区域荒漠和绿洲平衡共存。

关键词：土地利用转变规律驱动因素克里雅河

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A One-Dimensional Hybrid Simulation of DC/RF Combined Driven Capacitive Plasma

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Plasma Science and Technology 2012年第1期14卷 32-36页

作者： wang Shuai XU Xiang wang younian Department of Physics College of SciencesNortheastern UniversityShenyang 110891China School of Physics and Optoelectronic Engineering Dalian University of TechnologyDalian 116024China

We developed a one-dimensional hybrid model to simulate the DC/RF combined driven capacitively coupled plasma for argon discharges. The numerical results are used to analyze the influence of the DC source on the plasma density distribution, ion energy distributions （IEDs） and ion angle distributions （IADs） on both the RF and DC electrodes. The increase in DC voltage drives more high-energy ions to the electrode applied to the DC source, which makes the IEDs at the DC electrode shift towards higher energy, and the peaks in the IADs shift towards small angle regions. At the same time, it also decreases the ion energy at the RF electrode and enlarges the incident angles of the ions, which strike the RF electrode.

关键词： capacitively coupled plasmas DC/RF combined driven hybrid model IEDs IADs

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Effect of Duty Cycle on the Characteristics of Pulse-Modulhted Radio-Frequency Atmospheric Pressure Dielectric Barrier Discharge

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Plasma Science and Technology 2012年第12期14卷 1069-1072页

作者： LI Xuechun wang Huan DING Zhenfeng wang younian School of Physics and Optoelectronic Technology Dalian University of TechnologyDalian 116024 China

Using a one-dimensional fluid model, the pulse-modulated radio-frequency dielectric barrier discharge in atmospheric helium is described. The influences of the pulse duty cycle on the discharge characteristics are studied. The numerical results show that the dependence of discharge characteristics on the duty cycle is sensitive in the region of around 40% duty cycle under the given simulation parameters. In the case of a larger duty cycle, the plasma density is higher, the discharge becomes more intense, but the power consumption is higher. When the duty cycle is lower, one can get a weaker discharge, lower plasma density and higher electron temperature in the bulk plasma. In practical applications, in order to get a higher plasma density and a lower power consumption, it is more important to choose a suitable duty cycle to modulate the RF power supply.

关键词： pulse-modulation simulation radio-frequency atmospheric pressure dielectric barrier discharge

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Conductivity effects during the transition from collisionless to collisional regimes in cylindrical inductively coupled plasmas

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Plasma Science and Technology 2022年第5期24卷 118-133页

作者： Wei YANG Fei GAO younian wang College of Science Donghua UniversityShanghai 201620People’s Republic of China School of Physics Dalian University of TechnologyDalian 116024People’s Republic of China

A numerical model is developed to study the conductivity effects during the transition from collisionless to collisional regimes in cylindrical inductively coupled argon plasmas at pressures of 0.1-20 *** model consists of electron kinetics module,electromagnetics module,and global model *** allows for self-consistent description of non-local electron kinetics and collisionless electron heating in terms of the conductivity of homogeneous hot *** results for non-local conductivity case are compared with predictions for the assumption of local conductivity *** densities and effective electron temperatures under non-local and local conductivities show obvious differences at relatively low *** increasing pressure,the results under the two cases of conductivities tend to converge,which indicates the transition from collisionless to collisional *** relatively low pressures the local negative power absorption is predicted by non-local conductivity case but not captured by local conductivity *** two-dimensional(2D)profiles of electron current density and electric field are coincident for local conductivity case in the pressure range of interest,but it roughly holds true for non-local conductivity case at very high *** addition,an effective conductivity with consideration of non-collisional stochastic heating effect is *** effective conductivity almost reproduces the electron density and effective electron temperature for the non-local conductivity case,but does not capture the non-local relation between electron current and electric field as well as the local negative power absorption that is observed for nonlocal conductivity case at low pressures.

关键词： inductively coupled plasmas conductivity effects electron kinetics plasma parameters electromagnetic wave characteristics electrodynamics

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Multi-layer structure formation of relativistic electron beams in plasmas

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Plasma Science and Technology 2022年第2期24卷 10-16页

作者： Xiaojuan wang Zhanghu HU younian wang School of Physics Dalian University of TechnologyDalian 116024People's Republic of China

A two-dimensional electromagnetic particle-in-cell simulation model is proposed to study the density evolution and collective stopping of electron beams in background *** show here the formation of the multi-layer structure of the relativistic electron beam in the plasma due to the different betatron frequency from the beam front to the beam ***,the nonuniformity of the longitudinal wakefield is the essential reason for the multi-layer structure formation in beam phase *** influences of beam parameters(beam radius and transverse density profile)on the formation of the multi-layer structure and collective stopping in background plasmas are also considered.

关键词： multi-layer structure beam phase space relativistic electron beam plasma based beam dump PIC

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Feature Profile Evolution During Etching of SiO_2 in Radio-Frequency or Direct-Current Plasmas

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Plasma Science and Technology 2012年第1期14卷 64-70页

作者： ZHAO Zhanqiang DAI Zhongling wang younian School of Physics and Optoelectronic Technology Dalian University of TechnologyDalian 116024China

We have developed a plasma etching simulator to investigate the evolution of pattern profiles in SiO2 material under different plasma conditions. This model focuses on energy and angular dependent etching yield （physical sputtering in this paper）, neutral and ion angular distributions, and reflection of ions or neutrals on the surface of a photoresist or SiO2. The effect of positive charge accumulation on the surface of insulated mask or SiO2 is studied and the charge accumulation contributes to a deflection of ion trajectory. The wafer profile evolution has been simulated using a cellular-automata-like method under radio-frequency （RF） bias and direct-current （DC） bias, respectively. On the basis of the critical role of angular distribution of ions or neutrals, the wafer profile evolution has been simulated for different variances of angles. Observed microtrenching has been well reproduced in the simulator. The ratio of neutrals to ions has been considered and the result shows that because the neutrals are not accelerated by an electric field, their energy is much lower compared with ions, so they are easily reflected on the surface of SiO2, which makes the trench shallower.

关键词： profile evolution RF bias reflection etching yield

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Magnetic probe diagnostics of nonlinear standing waves and bulk ohmic electron power absorption in capacitive discharges

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Plasma Science and Technology 2021年第11期23卷 74-83页

作者： Kai ZHAO Yongxin LIU Quanzhi ZHANG Demetre J ECONOMOU younian wang Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024People's Republic of China Plasma Processing Laboratory William A.Brookshire Department of Chemical and Biomolecular EngineeringUniversity of HoustonHoustonTexas 77204-4004United States of America

It is recognized that standing wave effects appearing in large-area,very-high-frequency capacitively coupled plasma(CCP)reactors cause center-high plasma *** a high-frequency magnetic probe,we present a direct experimental diagnostic of the nonlinear standing waves and bulk ohmic electron power absorption dynamics in low pressure CCP discharges for different driving frequencies of 13.56,30,and 60 *** design,principle,calibration,and validation of the probe are described in *** structures of the harmonics of the magnetic field,determined by the magnetic probe,were used to calculate the distributions of the harmonic current and the corresponding ohmic electron power deposition,providing insights into the behavior of nonlinear *** a low driving frequency,i.e.13.56 MHz,no remarkable nonlinear standing waves were identified and the bulk ohmic electron power absorption was observed to be *** harmonic magnetic field/current was found to increase dramatically with the driving frequency,due to decreased sheath reactance and more remarkable nonlinear standing waves at a higher driving frequency,leading to the enhancements of the ohmic heating and the plasma density in the bulk,specifically at the electrode *** a high driving frequency,i.e.60 MHz,the high-order harmonic current density and the corresponding ohmic electron power absorption exhibited a similar node structure,with the main peak on axis,and one or more minor peaks between the electrode center and the edge,contributing to the center-high profile of the plasma density.

关键词： capacitively coupled plasmas magnetic probe nonlinear standing waves ohmic heating

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Influence of magnetic filter field on the radio-frequency negative hydrogen ion source of neutral beam injector for China Fusion Engineering Test Reactor

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Plasma Science and Technology 2021年第11期23卷 185-192页

作者： Yingjie wang Jiawei HUANG Yuru ZHANG Fei GAO younian wang Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024People's Republic of China

In the design of negative hydrogen ion sources,a magnetic filter field of tens of Gauss at the expansion region is essential to reduce the electron temperature,which usually results in a magnetic field of around 10 Gauss in the driver region,destabilizing the *** magnetic shield technique is proposed in this work to reduce the magnetic field in the driver region and improve the discharge *** this paper,a three-dimensional fluid model is developed within COMSOL to study the influence of the magnetic shield on the generation and transport of plasmas in the negative hydrogen ion *** is found that when the magnetic shield material is applied at the interface of the expansion region and the driver region,the electron density can be effectively *** instance,the maximum of the electron density is 6.7×10^(17)m^(-3)in the case without the magnetic shield,and the value increases to 9.4×10^(17)m^(-3)when the magnetic shield is introduced.

关键词： radio-frequency negative hydrogen ion sources three-dimensional fluid model neutral beam injection

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