Growth of nano-crystalline diamond on single-crystalline diamond by CVD method

Nanocrystalline (NC) diamond films are grown by chemical vapor deposition on various single crystal diamond faces. Under conditions of NC diamond growth, the growing filmmorphology is reduced to two planes: {100} and {111}. The {100} planes are smooth and homoepitaxial layerby-layer growth occurs on them, whereas the NC film formed by twin crystalliteswith sizes of several tens and hundreds nanometers grows on {111} planes. Nitrogen impurity sharply increases the diamond growth rate.     

Diamond cleavage: importance to high pressure research

The extraordinary properties of diamond make it the number-one choice for anvils in high pressure experiments involving anvil cells. In much of the literature on the properties of diamond the only cleavage mentioned is {111}. However, experience has shown that diamond anvils made with their [001] axis oriented in line with the principal stress axis of the anvil or at a small angle to it often failed with flat faces having {110} orientations; a cleavage plane is reported in some publications. Analysis of the anisotropy of strength and Poisson ratio in diamond has shown that such orientations do, indeed, favor initial failure on {110} cleavage planes. This analysis, in conjunction with stereographic projections of the {111} and {110} cleavage planes, suggests that a 27° tilt of the [001] axis with respect to the linear stress axis by rotation around the [100] or [010] axis should provide significantly greater resistance to failure by cleaving.     

CVD金刚石薄膜孪晶形成的原子机理分析

采用X射线衍射技术、电子背散射衍射技术和扫描电镜分别观察了不同甲烷浓度条件下沉积的CVD自支撑金刚石薄膜的宏观织构、晶界分布和表面形貌. 研究了一阶孪晶在金刚石晶体{111}面生长的原子堆垛过程. 结果表明，由于一阶孪晶〈111〉60°的取向差关系以及{111}面的原子堆垛结构，使{111}面上容易借助碳原子的偏转沉积产生一阶孪晶. 低甲烷浓度时，碳原子倾向于在表面能较低的{111}面沉积，为孪晶的形成提供了便利，且高频率孪晶使薄膜织构强度减弱. 甲烷浓度升高使生长激活能较小的{001}面成为主要前沿生长面，因而只有〈001〉晶向平行薄膜法向的晶粒能够不断长大，因此孪晶形核概率明显减小. 另外，在薄膜中发现二阶孪晶，并对二阶孪晶的形成进行了分析. 关键词： 金刚石薄膜 孪晶 原子机理 取向差     

Simultaneous determination of mean pressure and deviatoric stress based on numerical tensor analysis: a case study for polycrystalline x-ray diffraction of gold enclosed in a methanol-ethanol mixture

It is known that the {100} and {111} planes of cubic crystals subjected to uniaxial deviatoric stress conditions have strain responses that are free from the effect of lattice preferred orientation. By utilizing this special character, one can unambiguously and simultaneously determine the mean pressure and deviatoric stress from polycrystalline diffraction data of the cubic sample. Here we introduce a numerical tensor calculation method based on the generalized Hooke's law to simultaneously determine the hydrostatic component of the stress (mean pressure) and deviatoric stress in the sample. The feasibility of this method has been tested by examining the experimental data of the Au pressure marker enclosed in a diamond anvil cell using a pressure medium of methanol-ethanol mixture. The results demonstrated that the magnitude of the deviatoric stress is ～0.07?GPa at the mean pressure of 10.5?GPa, which is consistent with previous results of Au strength under high pressure. Our results also showed that even a small deviatoric stress (～0.07?GPa) could yield a ～0.3?GPa mean pressure error at ～10?GPa.     

Picosecond-laser-induced structural modifications in the bulk of single-crystal diamond

Arrays of through laser-graphitized microstructures have been fabricated in type IIa single-crystal 1.2-mm-thick diamond plates by multipulse laser irradiation with 10-ps pulses at λ=532 nm wavelength. Raman and photoluminescence (PL) spectroscopy studies of the bulk microstructures have evidenced the diamond transformation to amorphous carbon and graphitic phases and the formation of radiation defects pronounced in the PL spectra as the self-interstitial related center, the 3H center, at 504 nm. It is found that the ultrafast-laser-induced structural modifications in the bulk of single-crystal diamond plates occur along {111} planes, known as the planes of the lowest cleavage energy and strength in diamond.     

高温高压下掺硼宝石级金刚石单晶生长特性的研究

本文在5.1—5.6 GPa,1230—1600℃的压力、温度条件下,以FeNiMnCo作为触媒,进行单质硼添加宝石级金刚石单晶的生长研究.借助于有限元法,对触媒内的温度场进行模拟.研究得到了FeNiMnCo-C-B体系下,金刚石单晶生长的P-T相图.该体系下合成金刚石单晶的最低压力、温度条件分别为5.1 GPa,1230℃左右.研究发现,在单晶同一{111}扇区内部,硼元素呈内多外少的分布规律.有限元模拟结果给出,该分布规律是由在晶体生长过程中,{111}扇区的增长速度逐渐减小所致.{111}晶向的晶体生长实验结果表明,硼元素优先从{111}次扇区进入晶体.研究发现,这是该扇区增长速度相对较快,硼元素扩散逃离可用时间短导致的.另外,同磨料级掺硼金刚石单晶生长相比,对于温度梯度法生长掺硼宝石级金刚石单晶,由于晶体的增厚速度较慢,即使硼添加量相对较高,也可以实现表面无凹坑缺陷的优质金刚石单晶的生长.     

高分辨X射线衍射研究杂质对晶体结构完整性的影响

用水溶液生长晶体的方法生长出了不同掺杂的Sr(NO₃)₂晶体.用电子探针研究了杂质在晶体中的分布情况.结果表明,杂质在晶体中存在扇形分凝,其中Ba在{100}扇形区的含量大于{111}扇形区,而Pb的分凝情况相反,在{111}扇形区的含量大于{100}扇形区.用高分辨X射线衍射摇摆曲线技术研究了纯的、掺Ba的和掺Pb的Sr(NO₃)₂晶体的完整性情况,并用X射线衍射动力学理论计算了完整Sr(NO₃ 关键词： 高分辨X射线衍射 杂质 水溶液晶体生长     

晶面结构非均匀性对金刚石晶形的影响

 不仅考虑表面能，同时也引入表面结构非均匀性自由焓G_stⁱ，通过热力学分析，解释了随着晶体的逐渐长大而{110}面常在金刚石的外形中消失的机理，并用逆推法计算了有关数值。     

Studying the effect of hydrogen on diamond growth by adding C10H10Fe under high pressures and high temperatures

In this paper, hydrogen-doped industrial diamonds and gem diamonds were synthesized in the Fe–Ni–C system with C₁₀H₁₀Fe additive, high pressures and high temperatures range of 5.2–6.2?GPa and 1250–1460°C. Experimental results indicate similar effect of hydrogen on these two types of diamonds: with the increasing content of C₁₀H₁₀Fe added in diamond growth environment, temperature is a crucial factor that sensitively affects the hydrogen-doped diamond crystallization. The temperature region for high-quality diamond growth becomes higher and the morphology of diamond crystal changes from cube-octahedral to octahedral. The defects on the {100} surfaces of diamond are more than those on the {111} surfaces. Fourier transform infrared spectroscopy (FTIR) results indicate that the hydrogen atoms enter into the diamond crystal lattice from {100} faces more easily. Most interestingly, under low temperature, nitrogen atoms can also easily enter into the diamond crystal lattice from {100} faces cooperated with hydrogen atoms.     

Structure of boron carbide after applying shear deformations under a pressure to 55 GPa

Transmission electron microscopy has been used to study the structural features of boron carbide treated in a high-pressure shear chamber with diamond anvils in the pressure range 25–55 GPa. Such a treatment has been shown to lead to the predominant crack formation along planes {10 11 } and {10 12} and also the formation of polytypes in the {10 11} planes and strain bands in the {10 12} planes.     

Reflection-pattern study of the anisotropy of the etching of gallium antimonide

An etchant has been found for the selective etching of gallium antimonide, and a study has been made of the anisotropy of the dissolution along the main crystallographic directions. The dissolution rates of the gallium antimonide faces obey $$v_{\left( {111} \right)B} > v_{\left( {1 \cdot 0} \right)} > v_{\left( {110} \right)} > v_{\left( {111} \right)A} .$$ An optical method has been developed for orienting gallium antimonide crystals on the basis of the main crystallographic planes. Reflection patterns from GaSb differ from those from gallium arsenide, germanium, and silicon.     

Growth and stability of carbon islands on platinum surfaces

Details of the growth of C(graphite) islands and their stability on Pt surfaces were studied by FEM, UHV-SEM and very high resolution scanning AES. Initial nucleation of the C occurs on dislocations in the curved high index surface areas. Above 1150 K these randomly distributed islands dissolve and face specific layers are formed on {110} which can extend along the 〈100〉 zones all the way to the {100} planes. The sequence of stability of graphite layers on Pt is: {110} > all other {hk0} on the 〈100〉 zone except {100} > {100} followed closely by {111}. Concerning this layer stability, epitaxial mismatch plays a subservient role to the dipole interaction between metal substrate and graphite layer.     

Atomically sharp 〈111〉 trihedral angle of a tungsten tip

The processes occuring in the course of heating of a tungsten tip in an electric field and resulting in the formation of the 〈111〉 trihedral angle at the intersection of three {011} closest packed planes in the crystal lattice of tungsten are investigated using field-emission microscopy, continuous-mode field-desorption microscopy, and high-temperature field evaporation microscopy. It is demonstrated that atomically sharp angles can be formed at temperatures above 2200 K in the absence of field evaporation. An atom forming the apex of the trihedral angle lies in the triangle of atoms arranged in the (111) plane. In the triangle, each atom is located at the intersection of the 〈111〉 close-packed atomic rows, which are the boundaries of the {011} planes forming the trihedral angle and the {112} planes forming the angle edges two rows in width.     

高长径比柱状金刚石的高温高压合成与机理研究

为了拓展金刚石的种类和解决金刚石工具使用过程中因把持力不足造成的使用寿命降低等, 在中国式六面顶压机上, 通过对FeNi触媒成分和工艺的优化, 成功合成出高质量长径比大于2.5, 平均粒度在0.8—1.0 mm的柱状金刚石晶体. 该晶体独特的形貌, 将极大改善金刚石工具的在使用过程中出现的"脱粒"现象. 另外, 实验中发现, 柱状金刚石晶体的生长速度也远大于传统晶体的生长速度. 采用扫描电镜(SEM)和能谱(EDS)等手段对柱状金刚石晶体及晶体周围触媒成分进行了表征; 结果表明, 柱状金刚石晶体在生长过程中存在{100}和{111}晶面拉长, 以及包覆在晶体周围的触媒成分偏析. 在此基础上, 阐明了柱状晶体生长机理.     

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.     

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.     

The initial oxidation of molybdenum: IV. Epitaxial growth of oxide on molybdenum

The oxide which grows in low oxygen pressure and at temperatures between 700 and 1000 K on molybdenum is shown to be MoO₂. The epitaxial relationships between the oxide and the metal (100), (110) and (111) surfaces are given. The epitaxial relationships of oxide on the molybdenum (100) and (110) surfaces are geometrically equivalent. The oxide grows on the (111) molybdenum surface with no major oxide plane parallel to the substrate. It is suggested that the epitaxy of MoO₂ on the (111) surface is a consequence of growth on {211} molybdenum facets. The atomic positions in the pairs of interfacial planes found are given. There is little agreement between the positions of ions in the oxide and substrate lattice sites. Only in the postulated case of MoO₂ on {211} Mo facets is a small misfit found.     

氮掺杂金刚石{100}晶面的缺陷发光特性

氮是金刚石中最常见的杂质之一, 其对金刚石的缺陷发光具有重要的影响. 氮可以与金刚石中的本征缺陷形成复合缺陷. 本文首先利用阴极射线发光照片(CL)对一个高温高压合成的氮掺杂金刚石进行表征, 发现{100}晶面为蓝色, 然后利用透射电子显微镜(TEM)对该晶面进行电子辐照及后续退火处理, 以引入本征点缺陷进而形成含氮的复合缺陷, 并利用低温光致发光光谱(PL光谱)表征其缺陷发光特性, 发现该晶面主要以氮-空位复合缺陷(NV中心)发光为主, 并伴随着较弱的503 nm发光. 关键词： 金刚石 缺陷 发光     

Kinetic features of the oxide formation on {111} polar planes upon anode treatment of <Emphasis Type="Italic">n</Emphasis>-GaAs

The mechanism and kinetics of anode destruction of {111} polar planes of n-GaAs and morphological features of forming oxide films in the potentiostatic mode of polarization in weakly acid solutions of electrolytes have been studied. It has been found that anode polarization of the gallium plane (111) Ga provides the formation of a porous structure of both the single-crystal matrix and oxide film, which has a planar topology. In this case, the pore density is always commensurable with the surface dope concentration. In contrast to the gallium plane, the anode polarization of the arsenic plane \(\overline {\left( {111} \right)} \) As provides the tangential mechanism of destruction of the semiconductor matrix and the island-type morphology of the oxide. Equal crystallographic orientation of islands is determined by the directive action of the family of oxidized planes \(\left\{ {1\overline {11} } \right\}\) GaAs. However, regardless of the crystallographic orientation of the polar plane, the forming oxide is represented by polycrystalline As₂O₃ and amorphous Ga₂O₃.     

Formation of bcc-Ni thin film on GaAs(100) substrate and phase transformation from bcc to fcc

Ni thin films are prepared on GaAs(100) single-crystal substrates at room temperature by using an ultra-high vacuum radio-frequency magnetron sputtering system. The growth behavior and the crystallographic properties are studied by in-situ refection highenergy electron diffraction and pole-figure X-ray diffraction. In an early stage of film growth, a metastable bcc Ni(100) single-crystal film is formed on GaAs(100) substrate, where the bcc structure is stabilized through hetero-epitaxial growth. With increasing the film thickness, fcc crystals coexist with the bcc(100) crystal. High-resolution cross-sectional transmission electron microscopy shows that the film consists of a mixture of bcc and fcc crystals and that a large number of planar faults exist parallel to the fcc(111) close-packed plane. The results indicate that the bcc structure starts to transform into fcc structure through atomic displacement parallel to the bcc{110} close-packed planes.