N2/Ti微空心阴极放电等离子体阴极溅射模拟

采用Monte Carlo方法模拟N2/Ti微空心阴极放电等离子体阴极溅射过程,其中,氮离子(N2+,N+)轰击阴极表面采用PIC/MC模型模拟.计算溅射钛原子的热化过程、钛原子的密度及其平均能量分布.结果表明,沿各方向溅射出的90%金属Ti原子所带的初始能量小于30 eV,其散射角主要分布在30°和60°之间;溅射Ti原子在离微空心阴极壁约0.04 mm处出现热化极大值.     

氮气射频放电与直流放电PIC/MC模拟的比较

建立氮气容性射频等离子体过程的PIC/MC模型,将模拟结果与直流放电进行比较.结果表明:射频等离子体粒子(e,N₂⁺,N⁺)的平均密度较直流放电约大-个量级,在射频电极附近粒子(e,N₂⁺,N⁺)的平均能量比直流放电阴极附近的能量低3倍左右;密度偏低的原子离子N⁺在两电极附近具较高的能量,能量较低的分子离子N₂⁺在放电空间具较高密度,N₂⁺的密度大约是N⁺的6倍;计算的电子能量几率分布与测量结果-致.     

宏观放电参数对快原子态氮(N+,Nf)的影响

采用氮直流辉光放电等离子体中快电子和重粒子(N₂⁺,N⁺,N_f)混合的蒙特卡罗方法,模拟研究了快原子态粒子(N⁺,N_f)的产生率及轰击阴极的能量分布随宏观放电参数(P,V)的变化规律.结果表明,存在一最佳放电条件,使阴极壁处粒子(N⁺,N_f)的粒子数密度大且能量高;当电压大于800V时,轰击阴极的活性粒子(N⁺,N_f),主要由N₂⁺-N₂离解过程产生,电压小于300V时,主要由e^--N₂离解过程产生,模拟结果与实验结果相符合.     

氮气辉光放电阴极鞘层重粒子输运过程研究

采用蒙特卡罗模拟对氮气辉光放电等离子体阴极鞘层内离子(N₂⁺,N⁺)和快中性分子(N_2f)的输运过程进行了研究,计算了阴极鞘层中离子(N₂⁺,N⁺)和快中性分子的能量及角分布的空间变化,较好地解释了实验结果.得到了氮气辉光放电等离子体阴极附近主要存在着能量较低的荷能分子、密度较低的高能原子离子及密度和能量居中的分子离子.诸粒子状态随放电条件而变化.模拟结 关键词：     

等离子体金属表面氮化中放电温度对氮原子态粒子的影响

采用快电子和重粒子(N₂⁺,N⁺,N_f)混合的Monte Carlo模型,研究了氮直流辉光放电等离子体金属表面氮化过程中.e-N_2s及N₂⁺-N_2s两种碰撞离解过程产生的原子态粒子(N⁺,N)的产生率和氮化粒子(N⁺,N_f)轰击靶表面的能量、粒子数密度及入射角分布随气体温度的变化规律.结果表明,使阴极靶处活性粒子(N⁺,N_f)的能量高且粒子数密度大,存在一个最佳放电温度;粒子(N⁺,N)的产生率及在靶表面的密度数都随着放电气体温度的升高而减少;有大量中性快原子N_f在工件表面小角入射,且粒子(N⁺,N_f)角分布受温度的影响很小.     

N_2空心阴极放电向微空心阴极放电转变的PIC/MC模拟

开发了氮空心阴极放电PIC/MC二维自洽模型。研究了N2传统空心阴极向微空心阴极放电转变过程中电势和电场的变化。结果表明,不同尺寸的空心阴极放电的电势及电场分布规律几乎类似,但空心阴极孔径减小且气压增加时,电场近似线性增加;典型微空心阴极电场比传统空心阴极放电电场约大3个量级;微空心阴极放电产生的电子,氮分子离子和氮原子离子的密度比传统空心阴极放电约大3个量级,且微空心阴极放电中,N2+密度比N+密度大8倍以上。     

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开发了氮空心阴极放电PIC/MC二维自洽模型。研究了N2传统空心阴极向微空心阴极放电转变过程中电势和电场的变化。结果表明,不同尺寸的空心阴极放电的电势及电场分布规律几乎类似,但空心阴极孔径减小且气压增加时,电场近似线性增加;典型微空心阴极电场比传统空心阴极放电电场约大3个量级;微空心阴极放电产生的电子,氮分子离子和氮原子离子的密度比传统空心阴极放电约大3个量级,且微空心阴极放电中,N2+密度比N+密度大8倍以上。     

带有射频偏压源的感性耦合Ar/O2/Cl2等离子体放电的混合模拟研究

在刻蚀工艺中,通常会在感性耦合等离子体源的下极板上施加偏压源,以实现对离子能量和离子通量的独立调控.本文采用整体模型双向耦合一维流体鞘层模型,在Ar/O₂/Cl₂放电中,研究了偏压幅值和频率对等离子体特性及离子能量角度分布的影响.研究结果表明:当偏压频率为2.26 MHz时,随着偏压的增加,除了Cl^-离子和ClO⁺离子的密度先增加后降低最后再增加外,其余带电粒子、O原子和Cl原子的密度都是先增加后基本保持不变最后再增加.当偏压频率为13.56和27.12 MHz时,除了Cl^-离子和Cl₂⁺离子外,其余粒子密度随偏压的演化趋势与低频结果相似.随着偏压频率的提高,在低偏压范围内(<200 V),由于偏压源对等离子体加热显著增加,导致了带电粒子、O原子和Cl原子的密度增加;而在高偏压范围内(>300 V),由于偏压源对等离子体加热先减弱后增强,导致除了Cl₂⁺离子和Cl^-     

工作压强对射频辉光放电H2/C4H8等离子状态的影响

利用辉光放电技术采用等离子体质谱诊断的方法研究了不同工作 压强下H₂/C₄H₈混合气体等离子体中 主要正离子成分及其能量的变化规律, 并分析了压强对H₂/C₄H₈混合气体的离解机理以及主要正离子形成过程的影响. 结果表明: 随着工作压强的增加, 碳氢碎片离子的浓度和能量均逐渐减小. 当工作压强为5 Pa时, H₂/C₄H₈混合气体等离子体中C₃H₅⁺相对浓度最大; 压强为10 Pa时, C₃H₃⁺相对浓度最大; 压强为15, 20 Pa时, C₂H₅⁺相对浓度最大; 压强为25 Pa时, C₄H₉⁺相对浓度最大. 对H₂/C₄H₈等离子体中的主要组分及其能量分布所进行的定性分析, 将为H₂/C₄H₈混合气体辉光放电聚合物涂层的工艺参数优化提供参考技术基础. 关键词： 辉光放电技术 等离子体质谱诊断 工作压强     

介质阻挡均匀大气压氮气放电特性研究

基于一维流体力学模型，对介质阻挡均匀大气压氮气放电特性进行了数值计算研究.模型中考虑了氮气中主要的电离、激发过程，所包含的粒子种类为e，N₂，N⁺₂，N⁺₄，N₂(a¹∑^-_u)，N₂(A³∑⁺_u).模拟结果显示，氮中的放电具有低气压下汤生放电的特性.放电电流幅度较小，放电过程中气体电压变化缓慢，电子密度远低于离子密度，而且最大值出现在阳极，电子不能在放电间隙中被俘获，不存在中性等离子体区，气体中的电场趋于线性变化.亚稳态N₂(A³∑⁺_u)和N₂(a¹∑⁺_u)在整个放电空间都具有非常高的密度，比电子密度高三个量级以上，亚稳态密度的最大值出现在阳极，这样的分布决定了放电的空间结构.放电所需的种子电子主要由亚稳态之间潘宁电离提供，这种机理使放电的电离水平较低，导致氮气中的放电只能是汤生放电.随着放电参数的变化，多电流峰放电也可在氮气中获得. 关键词： 大气压均匀放电 介质阻挡放电 数值模拟 氮气     

Secondary ion emission from Si under nitrogen ion bombardment

The yield and energy distribution of positive secondary ions emitted from Si under N₂⁺ ion bombardment were measured. The obtained mass peaks correspond to three types of secondary ion species, that is, physically sputtered ions (Si⁺, Si₂⁺), chemically sputtered ions (SiN⁺ Si₂N⁺) and doubly charged ions (Si²⁺). The dependence of secondary ion emission on the primary ion energy was studied in a range of 2.0–20.0 keV. The yields of physically and chemically sputtered ions were almost independent of the primary ion energy. The yield of the doubly charged ion strongly depended on the primary ion energy. The energy distribution of secondary ions of the three types showed the same dependence on the primary ion energy. The most probable energy of the distribution increased with the primary ion energy. On the other hand, for the energy distribution curves of sputtered ions, the tail factors N in E^?N were constant and showed a m/e dependence.     

Atomic nitrogen laser action in a hollow cathode discharge

Near-infrared laser action of nitrogen atoms was obtained in a hollow cathode discharge. Four laser lines at wavelengths of 1358.2, 939.3, 938.7, and 862.9 nm were observed in the cw mode. In addition, the laser line at 904.6 nm was observed in quasi-cw operation in the afterglow for the first time. It is supposed that resonant charge exchange between He⁺ and N₂ followed by predissociation of N ₂ ⁺ is an important way of populating the upper laser levels.     

Production of copper vapor in a pulsed hollow cathode discharge

Spectral emission from a pulsed Cu hollow cathode was investigated in relation to discharge current to gain information on the density of the sputtered Cu vapor and on the persistence time of the metastable and ground-state atoms. The cathode was excited with 250 μsec discharge pulses at current densities up to 1 A/cm², using He, Ne and Ar as buffer gases. The intensities of the emitted Cu I lines were found to depend strongly on the simmer current. In atmospheres of Ne or Ar, the intensities of the resonance lines exhibited characteristic maxima during the initial 20 μsec of the discharge pulses. The density of the sputtered Cu atoms was determined by absorption measurements using a second Cu hollow cathode as alight source.     

微空心阴极放电的流体模型模拟

采用流体模型研究了微空心阴极放电(MHCD)的特点，对放电中电场的形成，电子和离子的密度分布，电子能量分布进行了数值模拟.该计算是针对高气压，圆筒形阴极结构下的He放电.结果表明放电中存在空心阴极效应，从电子能量分布可以看出，放电中存在高能电子，放电空间的电场分布主要表现为径向电场.此外，通过改变气压，阴极孔径等参数计算出它们对放电的影响.分析表明减小孔径有利于负辉区更充分的重合.提高气压将缩短阴极位降区. 关键词： 微空心阴极放电 流体模型     

Effect of helium/argon gas ratio in a He-Ar-Cu<Superscript>+</Superscript> IR hollow-cathode discharge laser: modeling study and comparison with experiments

The He-Ar-Cu⁺ IR laser operates in a hollow-cathode discharge, typically in a mixture of helium with a few-% Ar. The population inversion of the Cu⁺ ion levels, responsible for laser action, is attributed to asymmetric charge transfer between He⁺ ions and sputtered Cu atoms. The Ar gas is added to promote sputtering of the Cu cathode. In this paper, a hybrid modeling network consisting of several different models for the various plasma species present in a He-Ar-Cu hollow-cathode discharge is applied to investigate the effect of Ar concentration in the gas mixture on the discharge behavior, and to find the optimum He/Ar gas ratio for laser operation. It is found that the densities of electrons, Ar⁺ ions, Ar_m ^* metastable atoms, sputtered Cu atoms and Cu⁺ ions increase upon the addition of more Ar gas, whereas the densities of He⁺ ions, He₂ ⁺ ions and He_m ^* metastable atoms drop considerably. The product of the calculated Cu atom and He⁺ ion densities, which determines the production rate of the upper laser levels, and hence probably also the laser output power, is found to reach a maximum around 1–5 % Ar addition. This calculation result is compared to experimental measurements, and reasonable agreement has been reached. Received: 14 October 2002 / Revised version: 28 November 2002 / Published online: 19 March 2003 RID="*" ID="*"Corresponding author. Fax: +32-3/820-23-76, E-mail: annemie.bogaerts@ua.ac.be     

Mass spectroscopic investigation of ionized compenents of vacuum-arc discharge plasma

Special features of the application of a mass spectroscopic method to analysis of ionized components of the plasma of a vacuum-arc discharge are discussed. The intensities of N⁺, O ₂ ⁺ , Ar⁺, TiN⁺, and TiO⁺ ions as functions of the pressure of the corresponding neutral gas and the magnitude of the magnetic-field strength on the cathode surface are measured. The average energy of the N⁺ and TiN⁺ ions as measured with an electrostatic probe is equal to ≈25 eV. The number of the N⁺, O⁺, TiN⁺, and TiO⁺ ions that emerge on the cathode and propagate in the direction of the substrate is tenths of a percent of the number of metal ions, which confirms the mechanism of reactive vacuum-arc coating forming directly on the substrate. Physico-Technical Institute Academy of Sciences of Belarus, 4, Zhodinskaya St., Minsk, 220730. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 674–678, September–October, 1997.     

Relative densities of hydrogen ion species in a hollow cathode glow discharge

Highly resolved Doppler shifted peaks of the hydrogen Balmer lines, resulting from charge exchange of H⁺, H₂⁺, and H₃⁺ with an H₂ gas target, were obtained without the need for a deconvolution procedure. This enabled the unambiguous determination of the chemistry of these hydrogen species in the units of mTorr pressure range. This was obtained from a gaseous discharge using a biconical hollow cathode that yielded a well collimated and monoenergetic beam.     

Electron energy loss spectra from polycrystalline Cr and Cr2O3 before and after surface reduction by Ar bombardment

Electron energy loss spectra (ELS) have been obtained from polycrystalline Cr and Cr₂O₃ before and after surface reduction by 2 keV Ar⁺ bombardment. The primary electron energy used in the ELS measurements was systematically varied from 100 to 1150 eV in order to distinguish surface versus bulk loss processes. Two predominant loss features in the ELS spectra obtained from Cr metal at 9.0 and 23.0 eV are assigned to the surface and bulk plasmon excitations, respectively, and a number of other features arising from single electron transitions from both the bulk and surface Cr 3d bands to higher-lying states in the conduction band are also present. The ELS spectra obtained from Cr₂O₃ exhibit features that originate from both interband transitions and charge-transfer transitions between the Cr and O ions as well as the bulk plasmon at 24.4 eV. The ELS feature at 4.0 eV arises from a charge-transfer transition between the oxygen and chromium ions in the two surface layers beneath the chemisorbed oxygen layer, and the ELS feature at 9.8 eV arises from a similar transition involving the chemisorbed oxygen atoms. The intensity of the ELS peak at 9.8 eV decreases after Ar⁺ sputtering due to the removal of chemisorbed oxygen atoms. Sputtering also increases the number of Cr²⁺ states on the surface, which in turn increases the intensity of the 4.0 eV feature. Furthermore, the ELS spectra obtained from the sputtered Cr₂O₃ surface exhibit features characteristic of both Cr⁰ and Cr₂O₃, indicating that Ar⁺ sputtering reduces Cr₂O₃. The fact that neither the surface- nor the bulk-plasmon features of Cr⁰ can be observed in the ELS spectra obtained from sputtered Cr₂O₃ while the loss features due to Cr⁰ interband transitions are clearly present indicates that Cr⁰ atoms form small clusters lacking a bulk metallic nature during Ar⁺ bombardment of Cr₂O₃.