A study of the contrast on growth striations in silicon by X-ray double crystal topography in the Laue case

The image of growth striations in Si formed by the double crystal X-ray topography in the Laue case (DCTL) is investigated. The results of the dynamical diffraction theory for crystals with small microdefects have been compared with the contrast behaviour determined experimentally. It has been found that the theory explains qualitatively the contrast on the striations and it has been demonstrated that the DCTL method is suitable for detection of the presence of small microdefects in growth striations. Since the paper completes a series of papers on X-ray topography of growth striations, some general conclusions are formulated concerning the applicability of the X-ray topographical methods to the investigation of the structure of the growth striations     

金刚石结构三维光子晶体带隙特性的研究

应用平面波展开法研究了三维光子晶体的带隙特性,得到了随着填充率及材料的变化带隙的变化规律,结果为三维光子晶体器件的开发提供了理论依据。     

Method of phase-dispersion introscopy

A method is described for studying the internal structure of noncrystalline objects which are weak x-ray absorbers. The method uses the conventional arrangement of plane-wave topography. The object to be investigated is immersed in a monochromatic pseudoplane wave formed by a highly asymmetric reflection off a perfect crystal or several crystals and introduces phase disruptions at the wave front. A perfect single crystal mounted behind the object in a Laue arrangement reveals these disturbances, forming a contrast image of the boundaries of the structural components of the object. The possibilities of the method are illustrated by photographs of objects of various natures. The features of the image contrasts are discussed and confirmed by experiments on test objects. Zh. Tekh. Fiz. 67, 68–77 (January 1997)     

直拉硅单晶原生微缺陷的观察

对沿<100>方向生长的p型和沿<111>方向生长的n型宏观无位错直拉硅单晶,用铜缀饰X射线形貌术和腐蚀法观察到两种不同类型的微缺陷,对n型硅单晶还观察到一种特殊组态的微缺陷。对观察到的微缺陷的分布、组态进行了初步的分析。本文首次采用X射线透射投影和截面形貌术对硅单晶原生微缺陷进行直接观察,获得了相应的微缺陷图。所观察到的微缺陷的组态、尺度、分布等与铜缀饰X射线透射形貌图所示结果一致。 关键词：     

X-ray diffraction study of silicon single crystals highly doped with boron

The section Lang method of X-ray diffraction topography in combination with X-ray diffractometry based on the Borrmann effect was previously shown to be effective for detection of cluster formation during the growth process of highly doped Si-Cz single crystals. In the present work, the same techniques have been used to choose the best condition of technological heat treatment of boron-doped silicon from the view-point of formation of microdefects. The concentration and average size of dislocation loops have been calculated for two conditions of standard heat treatment from the analysis of diffusion scattering. The distribution of dislocation loops along the growth axis and crystal diameter has been determined as well.     

三硼酸锂晶体中负晶的观察

采用光学显微镜、X射线形貌术以及激光散射层析等方法,对新型非线性光学材料三硼酸锂晶体中的一种特殊的包裹体——负晶进行观测和研究,揭示了它的本质和组成,探讨了它的形成机理。 关键词：     

三硼酸锂(LBO)单晶的位错研究

本文叙述新型无机非线性单晶三硼酸锂(LBO)中位错的X射线衍射形貌观测和鉴定结果,探讨了位错形成的结构影响因素。 关键词：     

Superheat of silicon crystals observed by live X-ray topography

In-situ observations of Si crystal growth and melting have been carried out by live X-ray diffraction topography. Superheated solid states beyond the melting point was observed for dislocation-free crystals with melting in their inside. Dislocations were found to impede superheat and to melt the crystal without an appreciable superheating. A slightly superheated state accompanying melting removes all dislocations including immobile ones by their climb motion. It is proposed that self-interstitials needed for the volume change by melting are supplied by climb of dislocations, in contrast to dislocation-free crystals creating the interstitials thermally. In real crystal growth, remelting occurs naturally by melt convection and acts to make the growing crystal dislocation-free.     

The fluid phenomena in the crystallization of the protein crystal

This paper reports that an optical diagnostic system consisting of Mach-Zehnder interferometer with a phase shift device and image processor has been used for study of the kinetics of protein crystal growing process. The crystallization process of protein crystal by vapour diffusion is investigated. The interference fringes are observed in real time. The present experiment demonstrates that the diffusion and the sedimentation influence the crystallization of protein crystal which grows in solution, and the concentration capillary convection associated with surface tension occurs at the vicinity of free surface of the protein mother liquor, and directly affects on the outcome of protein crystallization. So far the detailed analysis and the important role of the fluid phenomena in protein crystallization have been discussed a little in both space- and ground-based crystal growth experiments. It is also found that these fluid phenomena affect the outcome of protein crystallization, regular growth, and crystal quality. This may explain the fact that many results of space-based investigation do not show overall improvement.     

人工水晶-x面上巴西双晶的形成机制

本文以人工水晶-x面上的巴西双晶作为研究对象,在实验的基础上,利用X射线衍射形貌术和电子探针显微分析等手段,研究了双晶的形成机制,同时分析了Kern的双晶成核动力学理论的不足之处。作者提出了双晶界应变能势垒的概念,认为由于晶体的不完整性提高了晶体本身的能量状态,结果相对降低了应变能势垒的高度,使得双晶易于发生。本文结合晶体生长实验和晶体缺陷的测试,分析了双晶形成与籽晶取向、杂质、晶体缺陷的相互关系,着重指出缺陷对双晶形成的影响。本文还以凹入角生长机制讨论了双晶的发育。 关键词：     

Fibrillar crystals of isotactic polystyrene. I. Morphological aspects

Fibrillar crystals have been prepared by the crystallization of isotactic polystyrene from stirred solutions in 1,3,5-trimethylben-zene and cyclohexanol. Similar microfibrils have been prepared in the nascent state by the polymerization of styrene in 1,3,5-trimethyl-benzene with a heterogeneous Ziegler-Natta catalyst. The microfibrils varied in width between 140 and 250 Å and were characterized by periodic lamellar overgrowths which were believed to give rise to a discrete X-ray reflection having a d-spacing of 90 A. Thermal analysis suggested that high growth temperatures favored greater crystal perfection. During crystallization from stirred cyclohexanol solutions, a fractionation of high molecular weight chains occurred which was more efficient at higher crystallization temperatures. In comparison to crystallizations under quiescent conditions, a marked facility of the crystallization process was observed in the formation of stirrer-crystallized and Ziegler-Natta polystyrene. The ease of crystallization of the shear-regenerated and nascent microfibrils has been related to a reduction in the free energy of nucleation. Mechanisms have been proposed to account for a favored nucleation process.     

色谱光谱法测试超临界压力下穿心莲内酯的结晶规律

以30%和95%的穿心莲内酯为实验原料,采用超临界CO2萃取结晶法考察了不同压力下穿心莲内酯在结晶板上的分布规律,同时也考察了晶体的晶型和红外光谱的变化规律。研究证实： 高效液相色谱分析,不同压力下穿心莲内酯在结晶板上都按纯度梯度结晶分布;X射线衍射分析,压力越高,晶体越趋于向比较单一的晶面上择优生长;红外光谱分析,压力的变化,并没有引起穿心莲内酯化学结构的改变。     

X射线截面形貌术中衍衬干涉条纹的消衰现象

用X射线衍射截面形貌术研究了金刚石晶体中Pendellosung条纹的消衰(fading)现象。实验表明,在尖劈形晶体和平板状晶体以及包含一片层错的晶体中都观察到动力学衍衬干涉条纹的消衰现象。用动力学理论和实验结果进行定量的比较,结果是一致的。 关键词：     

The mass transfer process and the growth rate of NaCl crystal growth by evaporation based on temporal phase evaluation

The mass transfer process and the crystal growth rate have been proved to be very important in the study of crystal growth kinetics, which influence the crystal quality and morphological stability. In this paper, a new method based on temporal phase evaluation was presented to characterize the mass transfer process in situ and determine the crystal growth rate. The crystallization process of NaCl crystal growth by evaporation was monitored in situ by a Mach-Zehnder interferometer, and the absolute concentration evolution, the evaporation rate and the real-time supersaturation of solution were obtained using temporal phase analysis, which acted as a novel technique to extract phase variation along time axis recently. Based on the evaporation rate and the absolution concentration, a new method to calculate mass transfer flux during the crystal growth without the knowledge of the mass transfer coefficient was proposed, and then the crystal growth rate could also be retrieved under the hypothesis of cubic crystals. The results show that the crystal growth rate increases with the supersaturation linearly. It is in agreement with the diffusion theories, which presume that matter is deposited continuously on a crystal face at a rate proportional to the difference in concentration between the points of deposition and the bulk of solution. The method is applicable to the research of crystallization process based on evaporation or vapor diffusion of which the precise conditions of nucleation and supersaturation are usually unknown because of the complexity of the evaporation rate and crystal growth rate.     

X-ray topography of diamond crystals in quasi-forbidden reflections

The X-ray topographs of diamond crystals of different perfection degrees have been obtained using the quasiforbidden 222 reflection. It has been shown that the use of such reflections in X-ray topography makes it possible to study the distribution of the defects affecting the electron density distribution over the crystal cross section.     

Phase matching,X-Ray topography,optical and thermal analysis of L-alanine cadmium chloride monohydrate: a nonlinear optical material

A potential semiorganic nonlinear optical material, L-alanine cadmium chloride monohydrate has been successfully synthesised and single crystals have been grown by slow evaporation solution growth technique at room temperature by using double distilled water as the solvent. The lattice dimensions of the grown crystal have been analysed by adopting powder X-ray diffraction technique and found that it crystallised in monoclinic system with space group C2. The crystalline perfection of the as-grown crystal has been assessed by high resolution X-ray diffraction and X-ray topography techniques and observed that the quality of the grown specimen is reasonably good. Its optical properties were examined by UV–Vis and photoluminescence techniques and found that there is no absorption in the entire visible range. Its functional groups were identified from FT-Raman and observed that there is no incorporation of other impurities during crystallisation. Its relative second harmonic generation efficiency has been tested with different particle size by Kurtz powder technique and found that within the coherence length the title compound is phase matchable. Its various thermal properties like thermal conductivity, specific heat, thermal effusivity, etc. have been evaluated by photopyroelectric technique and compared with other organic and inorganic materials. To confirm its piezoelectric response, its piezoelectric charge coefficient was measured using piezometer and found low. Its optical homogeneity as well as birefringence measurement of the grown specimen has been carried out by interferometric technique. The surface defects of the grown LACCM single crystal were analysed with etching at room temperature using water as an etchant.     

α—SiC晶体中的位错

用腐蚀法和X射线形貌术研究了α-SiC晶体中的位错。所用的腐蚀剂为熔融氢氧化钾。证实了尖底蚀坑与位错的一一对应关系。由于[0001]方向的螺型位错的Burgers矢量比刃型位错的Burgers矢量大得多,故可从蚀坑的深浅来判别螺型位错和刃型位错。给出了蚀坑形状和多型体晶体结构的对应关系。研究了表面生长蜷线的形态与SiC晶体中的位错及位错运动的关系。X射线形貌图显示了α-SiC晶体中相当数量的位错处于基面C面上。生长位错从晶体“根部”成核并随着晶体生长前沿的向前推进而延伸,因而位错线的方向常常沿[101O]和[1120]方向。将腐蚀法和X射线形貌术结合起来才能全面显示α-SiC晶体中的位错。 关键词：     

Analysis of dislocation images in X-ray topography of protein crystals: tetragonal hen egg-white lysozyme crystals

Dislocation images in X-ray topography of protein crystals such as tetragonal hen egg-white lysozyme crystals were analyzed. Not only extinction but also double contrast of dislocation images are clearly observed on the X-ray topographs. It should be noted that the observed image widths of the dislocation contrasts are much less than those calculated on the basis of the kinematical theory in X-ray topography, which has been successfully applied for inorganic crystals and organic crystals of small molecules so far. Moreover, in tetragonal HEW lysozyme crystals, the rocking curve widths of the perfect crystal related to the kinematical theory are less than the measured ones by two orders of magnitude. This discrepancy is consistent with that in the image width of the dislocation contrast. From this correlation, it is suggested that the larger rocking curve width, or higher mosaicity, is mainly responsible for the observed image width in the grown crystals.     

GaAs/AlGaAs异质结的界面束缚二维激子效应

本文讨论了GaAs/AlGaAs异质结界面的H线发光及其性能。用双晶X射线衍射及皮秒光致发光证明了H线与界面质量密切相关,并且有相似于激子跃迁的寿命行为。用限制于异质结界面势阱的二维电子(或空穴)与分布于GaAs边的三维空穴(或电子)组成的二维激子效应,解释了H线的实验结果。并讨论了不同外延生长的异质结与界面有关的发光行为。     

低温偏硼酸钡(BBO)单晶包裹物的X射线形貌衬度

本文叙述低温相偏硼酸钡β-BaB₂O₄(BBO)单晶包裹物的两套等三角锥形X射线形貌衬度,并且讨论了其衬度的主要来源。 关键词：