集中力作用下硅中位错结构

本文用化学侵蚀法研究了硅单晶样品在800—1000℃印压得到的位错“花结”。实验结果说明:印压产生的位错分布在{111}滑移面上;位错线的取向大部分是<110>或<112>方向。分析并观察到在压印下有两种位错环,一种是柏格斯矢量沿<110>方向并平行于(111)印压面;一种是柏格斯矢量沿<110>方向并与印压面相交。对位错环的结构进行了分析。     

Diffuse x-ray scattering study of the formation of microdefects in heat-treated dislocation-free large-diameter silicon wafers

Diffuse x-ray scattering (DXS) is used to study the formation of microdefects (MDs) in heat-treated dislocation-free large-diameter silicon wafers with vacancies. The DXS method is shown to be efficient for investigating MDs in silicon single crystals. Specific defects, such as impurity clouds, are found to form in the silicon wafers during low-temperature annealing at 450°C. These defects are oxygen-rich regions in the solid solution with diffuse coherent interfaces. In the following stages of decomposition of the supersaturated solid solution, oxide precipitates form inside these regions and the impurity clouds disappear. As a result of the decomposition of the supersaturated solid solution of oxygen, interstitial MDs form in the silicon wafers during multistep heat treatment. These MDs lie in the {110} planes and have nonspherical displacement fields. The volume density and size of MDs forming in the silicon wafers at various stages of the decomposition are determined.     

Dislocations in Fe-3% Si alloy single crystals deformed at a higher rate

The method of etching dislocations is used to study the distribution of dislocations and twins in Fe-3% Si alloy single crystals prepared from the melt after plastic deformation with higher speed. The crystals are deformed by twinning in the 〈111〉 directions along the {112} planes and by slip in the 〈111〉 directions along the {110} planes. The results prove that the dislocations causing plastic deformation move in the {110} planes during both fast and slow deformation. The difference in the slip surfaces during fast and slow deformation is explained by the different number of cross slips per unit dislocation path.     

Blocking-Effekte bei Transmission von α-Teilchen durch Germanium- und Siliziumkristalle

The energy loss of channeled and blocked α-particles of ThC transmitted parallel to the {111} and also the {110} planes of germanium and silicon was investigated. In the spectrum of the transmittedα-particles measured with a small-acceptance-angle detector, in addition to the random and normally channeled α-groups a separated group with a high energy loss was observed in the direction of the {111} planes, while in the direction of the {110} planes this group is not well separated from the randomα-group. A model is proposed which describes this high energy loss for observation in the direction of either plane. In agreement with this model a higher yield ofα-particles with high energy loss in the {111} planes in comparison with the {110} planes of germanium and silicon was measured.     

Two modes of slip systems in iron silicon crystals

Single crystals of iron 11·6 wt.% silicon were deformed in compression and slip bands were observed by optical microscope in specimens of different orientations. The deformation took place mostly by crystallographic slip along {110} planes, however, non-crystallographic slip in specimens of particular orientations was observed, too. On the basis of the present and previous results a simple qualitative model is proposed which explains which slip planes should be observed in crystals of iron with different silicon content deformed under various conditions. The main idea of the model is the eixstence of two different modes of slip systems in these crystals. The model predicts the conditions at which one slip mode prevails.The author would like to thank Dr. F. Kroupa, Dr. A. Gemperle, Dr. B. esták and Dr. J. Blahovec for useful discussions.     

钼单晶体的范性形变

在本文中,用金相和X射线方法,研究了24个取向不同的钼单晶体在-80℃(-50℃)、27℃、1000℃和～2000℃拉伸后的情况。分析研究的结果,认为观察到的{112}、{123}、{145}等滑移痕迹,是由于在两组不平行的{110}面上,沿着同一个<111>方向组合滑移后构成的外观面貌,而滑移面是密排的{110}面。外观滑移面(从滑移痕迹测定出的)会随样品取向不同而发生变化。当变形温度改变时,同一个样品的外观滑移面可能改变,也可能不改变,这要由样品的取向来决定。 关键词：     

The effect of shear stress on the screw dislocation core in bcc metals

The screw dislocation core structure in bcc metals under an external shear stress is investigated using the model of generalized splitting as an approximation of the Peierls-Nabarro model of screw dislocation dissociated on three {110} slip planes. The shear stress for which the core structure in this model is unstable is found.     

Crystallographic anisotropy in chemisorption: Nitrogen on tungsten single crystal planes

A molecular beam technique for the determination of sticking probabilities and surface coverages was used in earlier work to investigate the adsorption of nitrogen on tungsten {110}, {111} and {100} single crystal planes. In the present paper these studies have been extended to the {310}, {320} and {411} planes. Absolute sticking probabilities and adatom surface coverages are reported for crystal temperatures between 90 K and 960 K. Crystallographic anisotropy in this system is exemplified by zero coverage sticking probabilities with the crystal at room temperature: {110}, 1&#x0303;0^?2; {111}, 0.08; {411}, 0.4; {100}, 0.59; {310}, 0.72; {320}, 0.73. Results for planes on the [001] zone are quantitatively described by a general model developed for adsorption on stepped planes as an extension to the precursor-state order-disorder model for adsorption kinetics of King and Wells. It is shown that nitrogen dissociation only takes place at vacant pairs of {100} sites, but that subsequently the chemisorbed adatoms so formed may migrate out onto {110} terraces. The results are critically analysed in terms of the available LEED and work function data for nitrogen on tungsten single crystal planes, and the general model developed by Adams and Germer.     

Shock compression of [001] single crystal silicon

Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent with dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.     

Etch pits in AgCl crystals

Single crystal sheets have been prepared by the capillarity method. The dislocations can be revealed with a sodium thiosulphate solution at surface orientations from two regions in the basic triangle. These are: region A around 001 pole up to ≈25°, and region B around 111 pole up to ≈pa 10°. In the remaining region C of the basic triangle the dislocations do not etch. In region A the etch pits have the shape of pyramids. In region B they are triangular pyramidal in shape. Evidence is given that the edge and screw components of annealed and fresh dislocations are revealed by etching. At surface orientations near either the {00l} or {111} planes the slip can be activated in such zones 〈110〉 that are nearly parallel to the surface of the sheets. The slip bands are then straight and predominantly of the edge type.     

The topography of nickel crystals during the reaction towards Ni(CO)4; A field ion microscope study

The structural aspect of the formation of Ni(CO)₄ by the reaction of CO with solid nickel has been studied. The nickel initial state was a nearly hemispherical single crystal as prepared by field evaporation of a nickel field emitter tip. Field-free reaction of CO with the clean nickel surface took place at pressures up to 2 mbar, reaction times up to 45 h, and at a temperature of 373 K, which as a result from work by others was found optimum for highest rates of Ni(CO)₄ formation. Neon field ion imaging at 80 K after reaction with CO showed the crystal always in an intermediate state, which had the features: (1) Areas of {;111} were increased; (2) at half angles between a central (111) and peripherical {111} planes there were {110} planes flanked by {210}, and {100} flanked by {511}, respectively; (3) with the exception of the planes mentioned in feature (2), the remaining surface area was more than mono-atomically stepped. From these results and in accordance with the theory of crystal growth (Kossel, Stranski) and the theory of crystal dissolution (Lacmann, Franke, Heimann) a pure octahedron is expected to be the final state of the crystal. This implies that nickel atoms removed by the reaction are most frequently taken from 〈110〉 atom chains of the {111} planes.     

On slip in AgCl crystals at room temperature

At moderately wavy and branched slip bands on the surfaces of sheets of AgCl crystals the distribution of slip lines has been observed by means of the electron microscope. From the results it can be deduced that the cross slip of screw dislocations takes place. The divergence of the ends of slip bands has also been observed, which can be as well explained by the cross slip. From the active slip direction and the directions of straight slip lines in the cross-slip regions the microscopic slip planes have been determined. They lie in the region roughly limited by the {113} and {331} planes and the problem is discussed whether these planes are low-index crystallographic planes.     

Oxidation of tungsten single crystals in the presence of a high-electric field

The effects of high-electric fields on oxidation of tungsten single crystals in 6 × 10^?4 torr of oxygen at 1200–1500 °K were studied by field emission and transmission electron microscopy. Exposure of field emitters to oxygen in the absence of a field resulted in the build-up of emitter tips. Oxidation under the application of a negative or positive field, on the other hand, involved plane faceting and formation of oxide crystallites. Plane faceting was recognized to occur on the {111} and the {112} regions, showing the facetings of the {111} and the {112} planes into the {110} planes, whereas, crystallite formation seemed to take place selectively on the {100} regions. It was suggested by field emission microscopy that negative fields have an additional effect which causes the growth of an oxide crystal on the (110) plane. Transmission electron microscopy of an emitter oxidized in a negative field actually revealed a tiny oxide crystal with a size of ～ 300 Å grown on the developed (110) plane. The crystal exhibited a triangular shadow image strongly indicating an external pyramid-like form.     

Modelling the effect of pressure on the critical shear stress of MgO single crystals

A hierarchical multi-scale model was used to study the effect of high pressure on the critical shear stresses of MgO. The two main slip systems, ½?110?{110} and ½?110?{100}, were considered. Based on a generalised Peierls–Nabarro model, it is shown that the core structure of ½?110? screw dislocations is strongly sensitive to pressure. Mostly planar and spread in {110} at ambient pressure, the core of screw dislocations tends to spread in {100} with increasing pressure. Subsequently, an inversion of the easiest slip systems is observed between 30 and 60?GPa. At high pressure, the plasticity of MgO single crystals is expected to be controlled by ½?110?{100} slip systems, except at high temperature where both slip systems become active. Pressure is also found to increase the critical resolved shear stresses and to shift the athermal temperature toward higher temperatures. Under high pressure, MgO is thus characterised by a significant lattice friction on both slip systems.     

Specificity of defects induced in silicon by RF-plasma hydrogenation

Silicon wafers have been submitted to hydrogen RF-plasma treatment in various experimental conditions. Hydrogen RF-plasma treatment induced two kinds of effects on Si wafers, depending on the treatment conditions: surface corrugation and formation of structural defects below the free surface. Atomic force microscopy (AFM) investigations showed that the surface roughness significantly increased with the treatment duration, leading to the formation of pyramidal humps on the surface. The structural defects resulting after the plasma treatments were investigated by conventional and high-resolution transmission electron microscopy (CTEM and HRTEM) techniques. The specificity of the induced extended defects due to hydrogen decoration was emphasized. Three types of extended defects were identified and characterized: planar defects in the {111} and {100} planes and nanometric voids. Point defects related to the hydrogenation process were investigated by electron paramagnetic resonance (EPR) in correlation with the electron microscopy results.     

Shear band formation in IF steel during cold rolling at medium reduction levels

The mechanisms of shear band formation in IF steel after cold rolling to ～50% reductions have been investigated using transmission electron microscopy. The observations revealed that shear bands were always parallel to a second set of microbands, where these exist, and contained within individual crystals, indicating that shear banding is controlled by orientation. Crystallographic analysis revealed that shear banding involves two mechanisms, dislocation glide and rigid-body rotation. In the first step, dislocation glide causes a rotation about the 〈211〉 axis to produce the so called ‘S’ band, which gives the shear band its crystallographic character. In the second step, when the most heavily stressed slip plane parallel to the shear band is of the form {110}〈111〉, rigid-body rotation continues about the 〈211〉 axis in the sheared zone and, then, a rotation about the transverse direction (TD) is promoted by the geometry of the sample. Using rigid-body matrix theory, the calculated orientations of shear bands are shown to be in agreement with experimental observations. The process outlined is capable of explaining how slip processes in grains that contain microbands, using either {110} or {112} slip planes, can produce crystallographic shear bands.     

Effect of impurities on the growth of {113} interstitial clusters in silicon under electron irradiation

The growth and shrinkage of interstitial clusters on {113} planes were investigated in electron irradiated Czochralski grown silicon (Cz-Si), floating-zone silicon (Fz-Si), and impurity-doped Fz-Si (HT-Fz-Si) using a high voltage electron microscope. In Fz-Si, {113} interstitial clusters were formed only near the beam incident surface after a long incubation period, and shrank on subsequent irradiation from the backside of the specimen. In Cz-Si and HT-Fz-Si, {113} interstitial clusters nucleated uniformly throughout the specimen without incubation, and began to shrink under prolonged irradiation at higher electron beam intensity. At lower beam intensity, however, the {113} interstitial cluster grew stably. These results demonstrate that the {113} interstitial cluster cannot grow without a continuous supply of impurities during electron irradiation. Detailed kinetics of {113} interstitial cluster growth and shrinkage in silicon, including the effects of impurities, are proposed. Then, experimental results are analyzed using rate equations based on these kinetics.     

Study on titanium carbide field emitters by field-ion microscopy,field-electron emission microscopy,Auger electron spectroscopy,and atom-probe field-ion microscopy

Surface structure, composition, and some field-electron emission properties are examined for thermally annealed titanium carbide emitters. As a result of high temperature heating, low-index planes of {100} and {111} become facetted and are observed as dark areas in field-electron emission patterns. Electrons are emitted predominantly from the {110} planes. The surface composition becomes enriched with carbon when the carbon deficient titanium carbide, TiC_0.71, is heated at high temperatures in vacuum better than 10^?7 Pa. The topmost (110) layer consists of both Ti and C atoms. The instability in the electron emission current of titanium carbide is considered to be due to the local work function change caused by an interaction between vacuum residual gases and chemically active titanium atoms on the emitter surface.     

硅单晶中铜沉淀物的几何形态

本文利用红外显微镜和化学浸蚀的方法,研究了硅单晶中铜沉淀物的几何形态。实验表明,用红外显微镜观察到的各种形态的沉淀物是由{110}面上的片状沉淀组成的,样品的性质对它的形态没有影响。 关键词：     

直拉硅单晶原生漩涡缺陷的研究

本文用化学腐蚀方法, 从含有漩涡缺陷的原生CZ硅单晶中分离出尺寸在1000--6000埃间的氧沉淀, 制成萃取复型样品,用T E M 对氧沉淀作微区电子衍射分析. 同时, 观察硅薄膜中漩涡缺陷的TEM 象, 确定了二者的对应关系. 结果表明, 构成漩涡缺陷的氧沉淀主要是呈方形片的热液石英(keatite, siliea k) 及少量呈六角片的。方英石(a-cristobalite ), 沉淀片周边沿<1 1 0> 方向, 惯习面前者的为{ 100} , 后者的为{ 1 1 1}. 样品的红外吸收光谱表明, 方片状热液石英沉淀可能与1 2 2 4 (1/cm ), 吸收峰相对应. 关键词：