螺旋波等离子体的密度与离子能量分布的诊断

螺旋波等离子体是一种高密度的低温、低气压等离子体。这种等离子体在超大规模集成电路工艺，微机电系统加工、新型薄膜材料及纳米材料制备、材料表面改性以及气体离子激光器等方面具有广泛的应用前景。本采用一套球栅阻滞场带通式能量分析器，对螺旋波等离子体在工艺室扩散区样品架表面的特性进行了一些初步的实验研究，主要测试了在样品附近的等离子体在其表面上所形成的离子流密度（从而导出等离子体密度）以及入射离子的能量分布，并对这些参数随射频输入功率的变化进行了研究。研究发现，在螺旋波等离子体的扩散区，离子能量分布的宽度比用离子温度预期的值大得多，本定性地讨论了其原因。     

电子回旋共振等离子体用于聚四氟乙烯材料表面改性

在电子回旋共振 (ECR)等离子体装置中 ,使用Ar气 ,N2 气 ,H2 气和普通空气放电 ,对聚四氟乙烯 (PTFE)材料进行表面处理以提高其表面粘结性能。详细研究了在不同的放电气压 ,微波功率 ,处理时间 ,气体种类的情况下 ,样品表面的接触角的变化。同时也讨论了样品导电性能和外观等的变化。使用红外吸收谱对样品结构处理前后的变化进行了测量 ,对等离子体处理的机理进行了初步的讨论。使用Langmuir探针测量了Ar气和N2 气等离子体中的离子密度 ,用能量分析器测量了离子的能量。发现在对样品的处理中 ,ECR等离子体的离子密度是影响表面性能的主要因素 ,离子能量的作用不明显     

电子回旋共振等离子体用于聚四氟乙烯材料表面改性

在电子回旋共振（ECR）等离子体装置中，使用Ar气，N2气，H2气和普通空气放电，对聚四氟乙烯（PTFE）材料进行表面处理以提高其表面粘结性能，详细研究了在不同的放电气压，微波功率，处理时间，气体种类的情况下，样品表面的接触角的变化，同时也讨论了样品导电性能和外观等的变化，使用红外吸收谱对样品结构处理前后的变化进行了测量，对等离子体处理的机理进行初步的讨论，使用Langmuir探针测量了Ar气和N2气等离子体中的离子密度，用能量分析器测量了离子的能量，发现在对样品的处理中，ECR等离子体的离子密度是影响表面性能的主要因素，离子能量的作用不明显。     

磁场与密度对等离子体柱中螺旋波及能量沉积影响的数值研究

考察在高密度、强磁化径向非均匀等离子体柱中,在径向等离子体密度分布呈不同抛物线型轮廓及轴向静磁场不断增大的情况下,等离子体柱内右旋螺旋波与左旋螺旋波的传播性质及其径向、轴向能量沉积特性。采用数值方法求解基于Maxwell方程组的耦合波方程组,得到0.02~0.1 T磁场变化区间与n0=1.2×1013cm-3、α∈(0.36,0.83)径向等离子体密度分布条件下等离子体柱内m=±1角向模螺旋波场幅值及其径向、轴向能量分布情形.计算结果表明,α减小(0.83→0.36)、B0增大(0.02→0.1 T)时,m=+1模趋于r=0处附近传播,径向能量沉积变化极小,轴向能量沉积逐渐增强;m=-1模在一定B0范围内、α≈0.66时最大幅值传播,径向能量沉积趋向于等离子体柱表面附近,轴向能量沉积逐渐增强.其次,m=+1模较m=-1模场幅值与能量沉积均占主导地位;m=-1模能量沉积集中于天线电离区,m=+1模能量沉积远超于天线电离区。     

螺旋波等离子体源中离子能量及其诊断

介绍了一种具有广泛应用前景的新型等离子体源—螺旋波等离子体源,其特点是结构简单,可以产生高密度的等离子体.论文首先简述了螺旋波等离子体产生基本原理,并对螺旋波等离子体源的结构、加热机制以及天线形式与其能量耦合方式进行了介绍.然后,概述了螺旋波等离子体源的特性和诊断方式,主要介绍迟滞能量分析仪(RFEA)对螺旋波等离子体...     

等离子体浸没离子注入(PIII)过程中初始离子阵鞘层尺度内各物理量的时空演化

等离子体浸没离子注入(PIII)是用于材料表面改性的一种较新的、廉价的、非视线的技术.靶体被浸没在等离子体中,等离子体中的离子在靶体负脉冲偏压的作用下注入靶体而实现材料的表面改性.为了描述等离子体浸没离子注入过程,我们引用了一维粒子模型(PIC)对其进行了数值模拟,该模型通过求解空间电势的Poisson方程,电子的Bolzmann分布以及离子在网格中受力运动的Newton运动方程来完成.本文重点研究了一个初始离子阵鞘层内电势、离子浓度、离子注入靶体的速度和动能以及离子流密度的时空演化规律.     

方管内表面等离子体离子注入动力学GPU-PIC仿真

内表面改性近年日益受到人们重视。本文采用基于Graphic Processing Unit(GPU)的Particle-in-cell(PIC)模型对方形管内表面的离子注入动力学过程进行数值仿真研究。结果表明在注入过程中,辅助地电极周围形成离子空穴,随时间延长,离子空穴发生交联并不断扩展,直至所有离子注入到方管内壁。离子空穴的形成和扩展使得在管内部形成离子密度波,密度波的传播速度随时间增加。由于等离子体鞘层的不均匀重叠使得管内的初始鞘层厚度分布不均,其中位于拐角附近的鞘层较厚,从而又导致了方管内壁周向上的注入剂量和能量分布存在不均匀性,内壁平面附近位置的注入剂量和注入能量均相对较大,而拐角附近的离子注入剂量和能量最小。本文采用GPU加速PIC的算法取得了高达90的加速比,极大缩短了等离子体粒子模拟的计算时间。     

螺旋波等离子体研究进展

螺旋波等离子体为目前能产生最高等离子体密度的低温等离子体源之一,在低温等离子体应用领域中备受关注。螺旋波等离子体源具有电离效率高、电子密度高、约束磁场低、结构相对简单、可在极低气压下放电等优点,使其在集成电路工艺、薄膜沉积、刻蚀、表面改性和等离子体宇航推进等领域有着广泛的应用前景。本文综述了近年来螺旋波等离子体的主要研究进展,包括螺旋波等离子体的基本原理、耦合机制、低场峰现象、双电层结构等放电特性以及推进机制的研究进展,在此基础上展望了螺旋波等离子体未来的发展方向。     

均匀密度等离子体柱中螺旋波径向场型分布及能量分布数值研究

本文考察在高密度、强磁化径向密度均匀等离子体柱中,在径向等离子体密度量级及轴向静磁场数值不断增大的情况下,等离子体柱内右旋螺旋波与左旋螺旋波的电磁场幅值分布特性及径向模式能量分布特性。采用数值方法,求解基于m=-1方程组的耦合波方程组,得到2×10-2~9×10-2T磁场变化区间与1×10~(13)~9×10~(13)cm~(-3)径向等离子体密度量级变化条件下等离子体柱内右旋螺旋波与左旋螺旋波的场幅值及其径向能量分布情形。计算结果表明,轴向静磁场B0增大(2×10~(-2)~9×10~(-2)T),左旋螺旋波(LH-wave)场幅值减小,右旋螺旋波(RH-wave)场幅值增大,RH-wave与LH-wave径向能量幅值均减小;径向密度n_0增大,LH-wave场幅值增大,RH-wave场幅值减小,RH-wave与LH-wave径向能量幅值均增大;LH-wave能量峰值位置在距等离子体柱中心轴1/5半径处,而RH-wave能量峰值位置出现在中心轴附近处;B0约为几百高斯、n_0约为10~(13)cm~(-3)量级条件下,RH-wave总是较LH-wave在场幅值与能量沉积过程中占主导地位。     

工作气压对多脉冲鞘层动力学行为的影响

分别采用低压非稳态扩散流体模型和碰撞流体模型描述了等离子体浸没离子注入平面靶表面过程中等离子体回复扩散和鞘层演化行为,通过数值求解两流体模型研究了不同工作气压下多脉冲鞘层的时空演化动力学特征。计算结果表明,在连续脉冲作用下,开始几个脉冲内的注入离子流和离子碰撞能量较高,几百微秒内迅速降低并达到一个稳定值。多个脉冲作用后的离子注入参数稳定值比初始一个脉冲内的结果更准确,更具理论指导意义。工作气压对初始等离子体密度分布、注入离子流和离子碰撞能量影响显著。较低的工作气压无论对提高离子注入剂量还是离子碰撞能量都是十分有利的。     

用于空间辐射主动防护的等离子体发生器设计

等离子引发磁膨胀技术被美国航空航天局推荐为最有工程应用价值的空间辐射主动防护技术。在该技术中,高密度等离子体发生器的设计是其中的关键技术之一。本文设计了一种高密度螺旋波等离子体发生器,采用13.56 MHz射频源激发等离子体天线,并将该等离子发生器偏心放置在表面磁感应强度为0.1 T的柱状永久磁铁内,以氩气为工作气体进行了真空舱磁膨胀实验。利用朗缪尔探针,对发生器产生的等离子体密度及温度随输入功率的变化进行了测量,该发生器成功地引发了磁铁磁场膨胀。     

Generation processes of super-high-energy atoms and ions in magnetron sputtering plasma

Energy distribution function (EDF) of ion species (Ar⁺, Kr⁺, Xe⁺) in a rare gas magnetron plasma is measured at a substrate position, 0.1 m away from the target surface, by energy-resolved mass spectrometry. The measured ion EDF contains, besides a bulk low-energy part (<10 eV), a tail part of super-high energy on an order of 100 eV, depending on the mass ratio of ion species to target material (tungsten, permalloy (80% Ni, 20% Fe)). A weak electric field in a diffusion region of magnetron plasma cannot accelerate slow bulk ions of ∼0.2 eV to such high energies. Origin of large kinetic energies is attributed to the backscattering process on the target surface where, e.g., Ar⁺ ions impinging on the target are neutralized and reflected as fast Ar atoms of the kinetic energy approximately given by a two-body collision model. Subsequently, a part of fast atoms may be converted to fast ions in three possible collision processes in the diffusion region: (i) electron impact ionization (ii) resonant charge exchange, and (iii) ionization of slow atoms by fast atoms. Among them, the third process is found to be dominant from Monte Carlo simulations where the backscattering process is evaluated by the TRIM code. Furthermore, when the target mass is larger than the bombarding ion mass, the substrate is bombarded by the super-high-energy atoms having a flux 2-4 orders of magnitude larger than the fast-ion flux.     

Behaviour of neutral hydrogen atom density in the presence of a sample holder in a plasma reactor

The behaviour of density of neutral hydrogen atoms in the presence of a sample holder in a MESOX reactor was studied. The MESOX reactor is used for studying interaction of hydrogen atoms with solid state surfaces at extreme conditions. Concentrated solar radiation with power of approximately 6 kW is collimated to a spot with the surface in the order of magnitude 1 cm² thus allowing for independent sample heating above 2000 K. Hydrogen plasma is generated in a MW (microwave) discharge. The H-atom density is measured with a FOCP (Fibre Optics Catalytic Probe). The H-atom density in the empty reactor depends slightly on the pressure and MW power and is about 5 × 10²¹ m⁻³ at a power of 1000 W. The sample holder made from quartz glass was mounted in the centre of the reactor and the H-atom density was measured versus time. The H-atom density in the loaded reactor was decreasing continuously. After a time period in the order of 2 min, the H-atom density was reduced by approximately a factor of 3 in regards to the original value. The results were explained by taking into account a temperature dependence of the recombination coefficient for heterogeneous recombination of H atoms on the quartz surface.     

The Formation of Hollow Lead Structures on the Surface of PbSe Films Treated in Argon Plasma

Conditions for ion sputtering of a PbSe/CaF₂/Si(111) epitaxial system in high-density inductively coupled plasma of high-frequency low-pressure discharge in argon have been established that ensure the formation of submicron-sized hollow lead structures on a lead-selenide surface. The surface was plasma-treated for time periods within 60–240 s at low energy (20–30 eV) of Ar⁺ ions, which is close to their sputtering threshold energy. The properties of the obtained material were studied by the techniques of scanning electron microscopy and energy-dispersive X-ray microanalysis. It is shown that the characteristic size, shape, and density of surface structures can be varied within broad limits depending on the time of plasma treatment and temperature of the material surface. Physical processes responsible for the formation of hollow lead structures under the proposed conditions of plasma sputtering are considered.     

Effects of channel wall material on thrust performance and plasma characteristics of Hall-effect thrusters

The effects of channel wall material on Hall thruster performance and on plasma characteristics were investigated. A laboratory-model Hall thruster THT-III was operated with three channel wall materials of BN, BNSiN and BNAlN. Both the discharge current and the thrust were affected by the nature of the channel wall materials. The measured axial distributions of wall and plasma potentials, radial and axial electron temperatures, and electron number density near the channel walls showed that the wall material affected ionization region and ion wall loss in the channel, resulting from secondary electron emission, although ion acceleration region was determined by the axial distribution of radial magnetic field. The difference in discharge current between channel wall materials was attributed to the difference in axial current density near the inner channel wall, depending on secondary electron emission.     

Diffusion behavior of aluminum in the surface layer of iron processed by shot peening

An ultrafine-grained surface layer was fabricated on a pure Fe plate by the shot peening process. The average grain size within the surface layer of 10 μm thick is about 28 nm. The diffusion kinetics of Al was measured by secondary ion mass spectrometry within a temperature range of 300-380 °C. The diffusion coefficient of Al in the nanocrystalline layer is about 4 orders of magnitude higher than that in coarse-grained Fe. The activation energy of Al diffusion in nanocrystalline layer is 1.38 eV, which is much smaller than that reported for Al diffusion in the conventional Fe. The enhanced diffusivity of Al may originate from a considerable amount of nonequilibrium grain boundaries and a high density of dislocations in the surface layer processed by shot peening.     

Heating of polymer substrate by discharge plasma in radiofrequency magnetron sputtering deposition

The substrate used for the thin film deposition in a radiofrequency magnetron sputtering deposition system is heated by the deposition plasma. This may change drastically the surface properties of the polymer substrates. Deposition of titanium dioxide thin films on polymethyl methacrylate and polycarbonate substrates resulted in buckling of the substrate surfaces. This effect was evaluated by analysis of atomic force microscopy topography images of the deposited films. The amount of energy received by the substrate surface during the film deposition was determined by a thermal probe. Then, the results of the thermal probe measurements were used to compute the surface temperature of the polymer substrate. The computation revealed that the substrate surface temperature depends on the substrate thickness, discharge power and substrate holder temperature. For the case of the TiO₂ film depositions in the radiofrequency magnetron plasma, the computation indicated substrate surface temperature values under the polymer melting temperature. Therefore, the buckling of polymer substrate surface in the deposition plasma may not be regarded as a temperature driven surface instability, but more as an effect of argon ion bombardment.     

Ion energy distribution of an inductively coupled radiofrequency discharge in argon and oxygen

We report an experimental investigation of the ion energy distribution in an inductively coupled electron cyclotron wave resonance (ECWR) discharge with a superimposed static magnetic field. The inductively coupled discharge is sustained by applying a 13.56 MHz radiofrequency (RF) power to an aluminium single-turn coil located inside the vacuum chamber. The source region was separated by a grid from the diffusion region. Ion energy distribution (IEDF) measurements employing an energy-dispersive mass spectrometer or plasma process monitor (PPM) whose entrance opening was 15 cm away from the grid were performed in the diffusion region. The IEDF is composed of two peaks; a low-energy peak due thermalized ions and a high-energy peak due to ions coming directly from the source region without undergoing thermalization. The energetic difference between the groups thus reflects the plasma potential difference between the source region and the diffusion region. The pronounced intensity variation of the high-energy peak with increasing pressure is caused by charge-changing collisions yielding a depletion of the high-energy ions with increasing effective path length.     

Polymer pre-treatment by linear anode layer source plasma for adhesion improvement of sputtered TiN coatings

The pre-treatment of work-piece surfaces is decisive for improved adhesion of tribological, decorative, sensor, biocompatible, etc. coatings subsequently deposited by vacuum coating techniques. Most current industrial techniques (mainly glow discharges) miss the requirements for activating temperature-sensitive and electrically insulating materials. Gridless plasma sources like the linear anode layer ion source are an excellent alternative due to their low investment and operating costs and scalability to many industrial applications, and also due to the measured plasma characteristics (low surface charging, broad energy distribution). The appreciable increase of adhesion by anode layer source plasma pre-treatment and the effects of ion energy and gas composition are presented for room temperature sputtered titanium nitride coatings polyamide, polycarbonate, and poly(ethyleneterephtalate). For these polymers, the oxygen-based functionalization (chain-scissoring and cross-linking) strongly influence the wetting behaviour and improve the adhesion by suppressing adhesive cracking at low scratching loads. Low O₂ contents in Ar-O₂ discharge of ∼400 eV average ion energy lead to best coating adhesion.