Effect of Low-Frequency Power on Etching Characteristics of 6H-SiC in C4Fs/Ar Dual-Frequency Capacitively Coupled Plasma

Dry etching of 6H silicon carbide （6H-SiC） wafers in a C4Fs/Ar dual-frequency capacitively coupled plasma （DF-CCP） was investigated. Atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS） were used to measure the SiC surface structure and compositions, respectively. Optical emission spectroscopy （OES） was used to measure the relative concentration of F radicals in the plasma. It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency （LF） source. At lower LF power, a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers. At higher LF power the etching rate can be efficiently increased, but the surface roughness increases too. Compared with other plasma dry etching methods, the DF-CCP can effectively inhibit CχFγ films＇ deposition, and reduce surface residues.     

Effect of Low-Frequency Power on Etching Characteristics of 6H-SiC in C_4F_8/Ar Dual-Frequency Capacitively Coupled Plasma

Dry etching of 6H silicon carbide(6H-SiC)wafers in a C_4Fs/Ar dual-frequency capacitively coupled plasma(DF-CCP)was investigated.Atomic force microscopy(AFM)and X-ray photoelectron spectroscopy(XPS)were used to measure the SiC surface structure and compositions,respectively.Optical emission spectroscopy(OES)was used to measure the relative concentration of F radicals in the plasma.It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency(LF)source.At lower LF power,a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers.At higher LF power the etching rate can be efficiently increased,but the surface roughness increases too.Compared with other plasma dry etching methods,the DF-CCP can effectively inhibit C_xF_y films'deposition,and reduce surface residues.     

核电厂蒸汽发生器淤泥中主要金属元素的电感耦合等离子体发射光谱分析方法研究

核电厂蒸汽发生器淤泥组成成分及其变化趋势对二回路水化学工况控制起着重要的评价和指导作用。本文开发了湿法消解 电感耦合等离子体发射光谱联用分析方法,并将其应用于核电厂蒸汽发生器淤泥元素成分的定量分析。结果显示,淤泥中的主要元素有铝、钙、铬、铁、镁、锰、镍,各元素的质量分数为0.69%～67.76%。本方法的加标回收率为84.3%～110.7%,相对标准偏差不超过0.60%(n=7),方法的检测限为0.04～3.10 μg/L。     

Numerical and Experimental Investigation on the Attenuation of Electromagnetic Waves in Unmagnetized Plasmas Using Inductively Coupled Plasma Actuator

The attenuation of electromagnetic(EM) waves in unmagnetized plasma generated by an inductively coupled plasma(ICP) actuator has been investigated both theoretically and experimentally. A numerical study is conducted to investigate the propagation of EM waves in multilayer plasma structures which cover a square flat plate. Experimentally, an ICP actuator with dimensions of 20 cm×20 cm×4 cm is designed to produce a steady plasma slab. The attenuation of EM waves in the plasma generated by the ICP actuator is measured by a reflectivity arch test method at incident waves of 2.3 GHz and 10.1 GHz, respectively. A contrastive analysis of calculated and measured results of these incident wave frequencies is presented, which suggests that the experiment accords well with our theory. As expected, the plasma slab generated by the ICP actuator can effectively attenuate the EM waves, which may have great potential application prospects in aircraft stealth.     

Study on atomic layer etching of Si in inductively coupled Ar/Cl2 plasmas driven by tailored bias waveforms

Plasma atomic layer etching is proposed to attain layer-by-layer etching,as it has atomic-scale resolution,and can etch monolayer materials.In the etching process,ion energy and angular distributions (IEADs) bombarding the wafer placed on the substrate play a critical role in trench profile evolution,thus importantly flexibly controlling IEADs in the process.Tailored bias voltage waveform is an advisable method to modulate the IEADs effectively,and then improve the trench profile.In this paper,a multi-scale model,coupling the reaction chamber model,sheath model,and trench model,is used to research the effects of bias waveforms on the atomic layer etching of Si in Ar/C12 inductively coupled plasmas.Results show that different discharge parameters,such as pressure and radio-frequency power influence the trench evolution progress with bias waveforms synergistically.Tailored bias waveforms can provide nearly monoenergetic ions,thereby obtaining more anisotropic trench profile.     

Influence of Additive Gas on Electrical and Optical Characteristics of Non-equilibrium Atmospheric Pressure Argon Plasma Jet

Electrical and optical properties of an argon plasma jet were characterized. In particular, effects of an additive gas, namely nitrogen or oxygen, on these prop...     

Effects of Xe Gas Content and Total Gas Pressure on the Discharge Characteristics of Colour Plasma Display Panels

The effects of the Xe gas content and total gas pressure on the discharge characteristics of colour plasma display panels including the sustaining voltage margin, white-field chromaticity, discharge time lag （DTL）, discharge current peak, and full-width-at-half-maximum （FWHM） of the discharge current pulse, are experimentally studied. The results indicate that as the Xe gas content in the He-Ne-Xe gas mixture or total pressure increases, the sustaining voltage margin increases, the white-field chromaticity improves, and the discharge current peak has a maximum value, while DTL and FWHM have a minimum value. The mean electron energy in the gas mixture discharge is also calculated through a numerical solution of Boltzmann equation. The experimental results are explained from a view of the mean electron energy variations with the Xe gas content and total gas pressure.     

Experimental Study of the Movement of Particles in the Coupled Field of Low Temperature Plasma and Cyclone

An investigation was made of the movement of particles in the coupled field of a low temperature plasma and cyclone with PIV in order to study the moving trace of particles‘ movement in an electrostatic cyclonic collector. The experimental results show that the plasma field had little effect on the tangential velocity of particles, but had an obvious influence on the radial velocity. The tangential velocity of airflow had a great impact on particles‘ tangential movement. With the particles going down the cyclone tube, their tangential velocity dropped.Their radial velocity dropped as the radius enlarged from the center to the collecting wall of the tube. The plasma field could improve the radial velocity of particles by 5%-10%, but the motionalong the radius was determined by the cyclone.     

Effect of Gas Velocity on the Dust Sediment Layer in the Coupled Field of Corona Plasma and Cyclone

A dust sediment layer was found on the outer tube wall when the ESCP （electrostatic centrifugal precipitator） trapped diesel particulates or ganister sand. The Compton back scatter method was used to measure the sediment thickness during the experiment. The effect of the inlet gas velocity on the dust sediment layer was investigated. PIV （Particle Image Velocimetry） was used to measure the velocity field between the inner barb tube wall and the outer tube wail. Experiments showed that the thickness of the sediment increased with time, and the sediment layer at the lower end was much thicker than that at the upper end. The agglomeration on the outer tube wall could be removed when the inlet gas velocity was increased to a certain value.     

HL-2A芯部等离子体ITG模和TE模增长率研究

本文基于双流体模型,通过理论分析获得了芯部离子温度梯度(ITG)模和俘获电子(TE)模的色散关系。在Weiland模型的基础上,考虑了离子平行方向速度和TE的影响,计算了碰撞对ITG模和TE模增长率的影响。对HL-2A等离子体的计算结果表明,芯部等离子体的ITG模和TE模增长率与扰动波数密切相关,磁剪切对ITG模有明显的抑制作用。     

Experimental Study of the Unsteady Actuation Effect on Induced Flow Characteristics in DBD Plasma Actuators

The main aim of this paper is to investigate unsteady actuation effects on the operation of dielectric barrier discharge(DBD) plasma actuators and to study induced flow characteristics of steady and unsteady actuators in quiescent air.The parameters affecting the operation of unsteady plasma actuators were experimentally measured and compared with the ones for steady actuators.The effects of excitation frequency and duty cycle on the induced flow pattern properties were studied by means of hot-wire anemometers,and the smoke visualization method was also used.It was observed that the current and the mean induced velocity linearly increase with increasing duty cycle while they are not sensitive to excitation frequency.Furthermore,with increasing excitation frequency,the magnitude of vortices shedding from the actuator decreases while their frequency increases.Nevertheless,when the excitation frequency grows beyond a certain level,the induced flow downstream of the actuator behaves as a steady flow.However,the results for steady actuators show that by increasing the applied voltage and carrier frequency,the velocity of the induced flow first increases and then decreases with actuator saturation and the onset of the emission of streaky glow discharge.     

Influence of Ionization Degrees on Conversion of CO and CO_2 in Atmospheric Plasma near the Ground

A zero-dimensional model is used to study the processes of physical and chemical reactions in atmospheric plasma with different ionization degrees near the ground （0 km）. The temporal evolutions of CO, C02 and other main reactants （namely OH and O2）, which affect the conversion of CO and C02, are obtained for afterglow plasma with different initial values. The results show that the consumption rate of CO is largest when the initiM electron number density neo=1012 cm-3, i.e. the ionization degree is 0.000004%. The number density of CO2 is relatively small when neo=1016 cm-3, i.e. the ionization degree is 0.04%, whereas they are very close under the condition of other ionization degrees. Considering the total number densities of CO and C02 and the consumption rate of CO comprehensively, the best condition is neo=1013 cm-3, i.e. the ionization degree is 0.00004% for reducing the densities of CO and CO2 in the atmospheric plasma. The temporal evolutions of N＋, Ar＋, CO＋ and CO＋ are also shown, and the influences on the temporal evolutions of CO and C02 are analyzed with increasing ionization degree.