分子动力学模拟不同入射能量的CH与碳氢薄膜的相互作用

本文使用分子动力学方法模拟低能CH与碳氢薄膜的相互作用,以探讨在核聚变过程中CH的再沉积行为及对面向等离子体材料性质变化的影响。选择的入射能量分别为0.3,1,5,10 eV。模拟结果表明随着入射能量的增加C原子与H原子的吸附率增加,且在入射能量大于CH离解能的情况下,同一能量下H原子的吸附率小于C原子的吸附率。随着入射能量的增加,薄膜的厚度增加,薄膜中含有Csp2的范围变宽,并且表面逐渐转变为Csp2表面。薄膜中的C主要以Csp3形式存在,其次是Csp2,几乎不含Csp1。通过统计薄膜中的CHx(x为1~4)发现CH占优势,其次是CH2,而CH4的量非常少。     

F原子与Si表面相互作用的动力学研究

采用分子动力学方法模拟了F原子与Si表面相互作用,F原子入射能量分别为0.3,1,3,5,7和9 eV。在模拟过程中,F原子的沉积率与Si表面悬键密度有关,而Si原子的刻蚀率与表面晶格结构破坏程度有关,随着Si原子刻蚀率的增加,样品高度降低。在不同能量F原子作用下,样品Si表面形成Si-F反应层。Si-F反应层的厚度随入射能量的增加而增加,其组成成分对产物有至关重要的影响。     

分子动力学模拟不同入射能量的SiF2与SiC的相互作用

采用分子动力学模拟方法研究了入射能量对SiF2与SiC样品表面相互作用的影响。本次模拟选择的入射初始能量分别为0.3,1,5,10和25 eV。模拟结果显示SiF2分解率与Si和F原子的沉积率有密切的关系。沉积的Si和F原子在SiC表面形成一层SixFy薄膜。随入射能量的增加,薄膜厚度先增加后减小,薄膜中Si-Si键密度增大。构成薄膜的主要成分SiFx(x=1~4)中主要是SiF和SiF2,随入射能量的增加,薄膜成分由SiF2向SiF转变。     

CH与聚变材料Be相互作用的分子动力学模拟

采用分子动力学方法模拟了不同能量的CH粒子与聚变材料Be的相互作用。根据托卡马克中的环境,入射粒子CH的模拟入射能量分别设定为低能量(1,5,10,25 eV)和高能量(50,100,150,200 eV),其中碳的沉积率随能量的增大逐渐增加,而氢的沉积率恰好相反。当CH粒子的入射能量为低能量时,Be样品表面形成一层碳氢膜;且其膜厚度越来越薄,并且形成一个厚度逐渐增加中间层;当入射能量为高能量时,样品中的Be原子溅射越来越大,入射粒子在样品中的入射深度越来越深,对样品的破坏越来越大,且会在样品中形成一个C反应层。     

分子动力学模拟不同入射角度的SiF3+对SiC表面的作用

采用分子动力学模拟方法研究了300K入射能量150eV时,以不同角度(5°、30°、60°和75°)入射的SiF3+与SiC表面的相互作用过程。模拟中使用了用于Si-F-C体系的Tersoff-Brenner势能函数。模拟结果显示,入射SiF3+与SiC表面相互作用后会分解,分解率随着入射角度的增加而减小。分解产物除少量散射外,大部分会沉积在SiC表面,Si和F在SiC表面的平均饱和沉积量随入射角度的增加而减少。随着SiF3+不断轰击SiC表面,SiC表面会形成Si-F-C反应层,且反应层厚度随着入射角度的增加而减少。同时发现SiC中的Si原子较C原子更容易被刻蚀,与实验结果一致。当刻蚀达到稳定,入射角度为5°、30°、60°和75°时,C的刻蚀率分别约为0.026、0.038、0.018、0.005,Si的刻蚀率分别约为0.043、0.051、0.043和0.023。各入射角度下,产物分子种类主要为F、SiF和SiF2。F和SiF产物量随入射角度增加而增加,而SiF2产量随入射角度增加而减少。在入射角度等于5°和30°时,SixFyCz是主要的含C产物;而在入射角度等于60°和75°时,CF是主要的含C产物。在入射角度等于5°和30°时,SiF2是主要的含Si产物;在入射角度等于60°和75°时,SiF是主要的含Si产物。刻蚀主要通过化学增强的物理溅射进行。     

分子动力学模拟C+离子与聚变材料钨的相互作用

采用分子动力学方法模拟不同能量的C+离子与聚变材料钨的相互作用.模拟结果表明:当C+离子入射剂量为3.11×1016 cm-2,入射能量为50eV时,样品表面形成一层碳膜;而入射离子能量为150和250eV时,C+离子入射到样品内与钨原子共同形成碳钨混合层,样品表面没有形成碳膜;碳的沉积率随能量的增大先减小后增加,溅射率随能量的增大先增大后减小;轰击后的样品中,碳原子密度、C-W键密度及C-C键密度分布都随能量的增加逐渐向样品内移动,且C-W键分布厚度随能量的增加而逐渐增加,C-C键分布厚度几乎不随能量变化;在作用过程中极少量的钨原子发生溅射,但引起钨品格损伤严重;碳在轰击后的样品中主要以Csp3杂化形式存在.     

Ar~+与氟化的Si样品相互作用机制的研究:分子动力学模拟

采用分子动力学方法模拟了Ar+与表面含有C,F反应层的Si样品的相互作用过程,以了解Ar+与氟化的Si的作用机制。为了和相对应的实验结果做比较,选择了两种样品,表面富F样品和表面富C样品。模拟结果表明,对于表面富F样品,能清楚地看到Si的刻蚀且随着入射能量的增加Si的刻蚀增加。当入射Ar+数量到达一定程度后Si的刻蚀完全停止。对于富C样品,几乎没有发生Si的刻蚀,这是由于Si-C键对Si的刻蚀起阻碍作用。     

分子动力学模拟样品温度对F刻蚀SiC的影响

利用分子动力学模拟方法研究了在低能F原子刻蚀SiC表面过程中样品温度对刻蚀的影响。由模拟结果可知,随着温度的升高,F在样品表面的沉积量和散射量均呈下降趋势,而发生溅射的F的量和与样品作用生成挥发物质的F的量逐渐增加。Si的刻蚀量均随着温度的升高而升高。样品中Si原子的刻蚀主要是通过生成SiF4得以实现的,C原子的刻蚀主要是通过生成CFx(x=1～3)等挥发性物质实现的。     

石英微晶天平技术在原子层沉积碳化镍薄膜过程中的应用研究北大核心CSCD

采用等离子体增强原子层沉积技术分别以Ni(amd)2、Ni(dad)2为镍、碳前驱体,氢等离子体为还原剂成功沉积了碳化镍薄膜。两个沉积过程中,碳化镍薄膜厚度都随着反应循环次数的增加而线性增加。利用石英微晶天平技术对碳化镍薄膜的沉积过程进行了原位在线测量。初步提出碳化镍薄膜的沉积机理,其中由等离子体作用产生的氢原子对沉积过程有重要作用。一方面,在等离子体中原子氢与Ni(amd)2或Ni(dad)2发生化学反应,生成Ni、挥发性的N-叔丁基乙酰胺盐和碳氢化合物,这些镍在镍表面上有吸附和分解的趋势。此外,原子氢对吸附的碳氢化合物脱氢生成碳化镍和大量碳物种具有促进作用。另一方面,预计它还会刻蚀碳化镍表面的无定形碳和石墨,或者将碳化镍分解成具有催化活性的金属镍。     

低能大流强氢离子辐照对钨的刻蚀行为

在聚变相关的钨(W)偏滤器辐照下,研究了低能大流强氢(H)离子辐照对多晶钨材料的刻蚀行为。使用扫描电子显微镜(SEM)、导电原子力显微镜和基于SEM的电子背散射衍射等手段研究了大流强(~10²² ions/m²·s)、剂量为1.0×10²⁶ ions/m²、能量为5~200 eV的氢离子辐照对多晶W材料表面刻蚀行为的影响。结果表明,随着H离子辐照能量的增加W的溅射率迅速提高,W表面发生刻蚀后产生条纹状结构,而且同一晶粒上条纹的方向具有一致性,条纹两侧的缺陷分布明显不同,意味着W表面的刻蚀优先沿某一特定晶面方向进行。     

Prediction of etching results and etching stabilization by applying principal component regression to emission spectra during in-situ cleaning

A method to predict etching results by analyzing plasma emission spectra during in-situ cleaning was investigated, where the plasma emission spectra indicate the surface condition of etching reactor walls. Plasma-wall interaction was evaluated by using both principal component regression of plasma emission spectra and attenuated-total-reflection Fourier-transform infrared spectroscopy. We found that differences in the amount of silicon oxide deposition on the reactor wall affected radical composition in the plasma during in-situ cleaning and consequently affected the etching results. Etching result predictions using the plasma spectra corresponded very well to the etching result measurements, which are used to improve etching stability.     

Chemisorption of OH on the H-terminated Si(0 0 1) surface

In order to reveal the etching mechanism of the H-terminated Si(0 0 1) surfaces in ultrapure water, first-principles molecular dynamics simulations of H-terminated Si(0 0 1) surfaces interacting with OH molecules were carried out on the basis of density-functional theory. It was confirmed that the interaction between two OH molecules and the surface silicon atom on the step edge breaks the Si–Si back-bond and initiates the etching process.     

Vapor-solid-solid Si nano-whiskers growth using pure hydrogen as the source gas

This paper describes the growth mechanism and structure of Si whiskers grown on a Si substrate in a tungsten hot filament chemical vapor deposition reactor with pure hydrogen as source gas using a two step process. In the first step, atomic hydrogen etched the silicon surface, forming silicon hydrides that react with tungsten from the filament. The resulting silicide particles deposited on the silicon surface forming a mesh-like pattern. The particles work as an etching mask against hydrogen radical etching of the silicon surface and inverted-pyramids or V-groove-shaped surface texture were obtained. In the second step the filament current was reduced and whiskers grew onto the substrate due to the interaction of the silicon hydrides with the particles and subsequent precipitation of saturated Si. The whiskers were found to have tungsten silicide particles on their tip, suggesting the whisker growth was through the Vapor-Solid-Solid (VSS) mechanism. A balance between the hydrogen radical etching effect and the supply of silicon hydride from the etching reaction on the silicon surface is crucial for the growth of dense silicon whiskers.     

Surface wetting phenomena of plasma polymer-coated sheets of poly(l-lactic acid)/poly(butylene succinate)

Water-repellent surfaces were fabricated on blend sheets of poly(l-lactic acid)/poly(butylene succinate) with various blending ratios by the successive processing; (1) plasma etching, followed by (2) the hydrophobic plasma polymer coating. Rough morphology was formed effectively on the mosaic structured surface of blend sheets via the oxidative etching, and advanced water repellency was achieved after the thin membrane coating was synthesized with a hydrophobic plasma polymer coating by use of hexamethyldisiloxane or hexamethyldisilazane. High water repellency is expressed through the columnar hair-like structured model, where the air-water surface interaction in the voids is taken into account.     

Ratchet effect study in Si/SiGe heterostructures in the presence of asymmetrical antidots for different polarizations of microwaves

In this work, we studied the photovoltage response of an antidot lattice to microwave radiation for different antidot parameters. The study was carried out in a Si/SiGe heterostructure by illuminating the antidot lattice with linearly polarized microwaves and recording the polarity of induced photovoltage for different angles of incidence. Our study revealed that with increased antidot density and etching depth, the polarity of induced photovoltage changed when the angle of incidence was rotated 90 degrees. In samples with large antidot density and/or a deeply etched antidot lattice, scattering was dominated by electron interaction with the asymmetrical potential created by semicircular antidots. The strong electron–electron interaction prevailed in other cases. Our study provides insight into the mechanism of interaction between microwaves and electrons in an antidot lattice, which is the key for developing an innovative ratchet-based device. Moreover, we present an original and fundamental example of antidot lattice etching through the use of a two-dimensional electron gas. This system deals with a hole lattice instead of an electron depletion in the antidot lattice region.     

Poly-l -lactic acid modified by etching and grafting with gold nanoparticles

This work is focused on characterization of plasma treated and consequently etched and grafted biocompatible polymer poly(l-lactide acid) (PLLA). The interaction of biodegradable polymers with cold plasma is of a great importance in a tissue engineering and surface science. Cold plasma exposure, grafting with gold nanoparticles and etching processes were successfully applied to biopolymer substrate. A method for biopolymer nanostructuring as combination of cold plasma treatment and Au nanoparticle grafting for biocompatibility improvement is introduced. Surface roughness, morphology and surface chemistry was determined. The plasma modification leads to significant increase in surface roughness of PLLA and appearance of sharp spikes and ridges on the PLLA surface. Modification by grafting and etching leads to significant changes in PLLA surface morphology and chemistry. The surface ablation of PLLA has been proved to be significant. In etching of plasma-modified PLLA, methanol proves to be stronger etching agent than water. The grafting of PLLA with gold nanoparticles improved mouse embryonic fibroblasts (NIH 3T3) adhesion and proliferation significantly.     

Thermal annealing behaviour of Si/SiO2 structures

The interaction of vacuum-deposited silicon films with the underlying oxide at annealing temperatures of 1050–1250°C was studied by means of low energy electron diffraction, Auger spectroscopy, IR spectroscopy, and optical and electron microscopy. The deposition of silicon onto SiO₂-covered silicon substrates and the annealing of the samples was carried out in ultrahigh vacuum. The results obtained revealed that the silicon and oxide layers are etched away by heat treatment. The dependence of the etching on the thickness of the silicon film, the thickness of the SiO₂ layer and the annealing temperature was determined. A qualitative model of the etching process is proposed.     

光助电化学刻蚀法制作大面积高深宽比硅深槽

为解决用光助电化学刻蚀法制作大面积高深宽比硅深槽过程中出现均匀性差的问题,在分析了传统光助电化学刻蚀装置中存在的不足的基础上,设计并制作了一套新型大面积光助电化学刻蚀装置.该装置通过特殊设计的花洒式溶液循环机构和水冷隔热系统,解决了大面积硅片在长时间深刻蚀过程中出现的溶液升温和气泡堆积的问题.借助这套装置能够实现127 mm（5 inch）及以上大面积硅片的均匀深刻蚀.同时,通过采用以0.01 A/min的速率逐步增加刻蚀电流的方法,来补偿侧向腐蚀对槽底电流密度的影响,保证了整个刻蚀过程中硅深槽形貌的一致性.最终在整个127 mm硅片上制作出了各处均匀一致的硅深槽,深度达60μm、深宽比在20以上.     

Enhanced wet etching of patterned GaN with ion implantation

We present the enhanced wet etching of GaN epilayer implanted with Au+ ion. Patterned GaN with 2 microm-wide sink-like strips was achieved by using 500 keV Au+ ion implantation and KOH etching. The Dependence of etching depth on etching time for the implantation at different ion fluences was investigated. The experiment showed that the damaged GaN area could be almost etched out at high ion fluence, and the etching depth could exceed the project range of incident 500 keV Au+ ion. The etch pits could be observed at the bottom of the etched area. The -400 nm depth etching could be achieved with high fluence implantation after a long etching time, and the edge of etched area could remain clear until the etching process had passed 40 min. As-deposited SiO2 spheres were used to mask the GaN sample in implantation process to investigate the etching effect. -70 nm wave of the GaN surface was observed. The results of our experiments may suggest an approach to the fabricating of GaN devices.     

Interaction of Fine Fe Particles with Structural Defects on {111} Faces of Synthetic Diamond Crystals in a Hydrogen Atmosphere

Data are presented on the interaction of fine Fe particles with structural defects on the octahedral faces of synthetic diamond crystals during catalyzed diamond gasification in a hydrogen atmosphere at 900°C. The defects were revealed by etching in molten NaNO₃. The results indicate that the penetration of metal particles into the crystal bulk is only possible at the outcrops of screw dislocations. The density of such defects determines whether lateral (parallel to the face) or normal (perpendicular to the face) etching prevails.