Ⅱ-Ⅵ族应变层超晶格的X射线衍射分析

本文报导了用计算机控制的衍射仪(CuKα辐射)测量的金属有机化学汽相沉淀(MOCVD)方法生长的Ⅱ-Ⅵ族应变层超晶格的X射线衍射曲线,观察到了超晶格结构的多级卫星峰,且卫星峰的强度随角度呈周期性变化.对这种卫星峰形成包络的衍射曲线,用X射线运动学衍射理论进行了分析和讨论,这种讨论有助于理解X射线衍射曲线中卫星峰的形成.同时用光致发光和包络峰宽度的方法估算了样品的结构参数.     

X光能点、放大倍率及针孔尺寸对空间分辨的影响

X光针孔成像是惯性约束聚变(ICF)研究中重要的诊断方法,对其点扩散函数的计算可用于图像重建和系统空间分辨的判断。对菲涅耳衍射公式进行了化简,分析了X光能点、针孔尺寸及放大倍率对针孔点扩散函数的影响。实验在保证成像能获得足够高信噪比的条件下,通过模拟获得在最佳空间分辨时所要的针孔大小、放大倍率和X光能点等参数。在流体力学不稳定性的静态样品定标实验中,通过模拟获得了针孔的调制传递函数(MTF),结合实验测量的结果反推获得分幅相机本身的MTF值。同时采用测刀边函数的方法获得了分幅相机本身的刀边函数,进而得到相机在各空间频率下的MTF值。两种方法得到的分幅相机MTF值一致,验证了通过菲涅耳衍射模拟X光针孔成像的可行性。     

Solving modulated structures by X-ray and electron crystallography

X-ray diffraction can be used for accurately determining not only classical, ordinary structures, but also modulated ones. For structures with weak modulations, the modulation induced satellite reflections are often hard to be observed by X-ray diffraction, but they appear clearly in electron diffraction. In these cases, X-ray diffraction will give only average structures whereas electron diffraction will yield information about the modulations. Sr(1.4)Ta(0.6)O(2.9) is a complex modulated compound with weak modulation and small modulated domains. Here we demonstrate the power of combining X-ray and electron crystallography for studying modulated structures on powders. The modulations of Sr(1.4)Ta(0.6)O(2.9) were determined from electron diffraction (SAED) and high resolution electron microscopy (HREM) images. With specially developed image processing techniques, the weak modulations were enhanced, facilitating the interpretation of HREM images in terms of atomic structure.     

薄膜和多层膜的X射线散射方法与应用

文章主要介绍了几种X射线散射技术，包括X射线小角反射技术、X射线漫散射技术、掠入射X射线衍射和多晶薄膜的小角衍射技术。通过具体的事例说明这些X射线散射方法在薄膜研究中的应用。     

X-ray Bragg diffraction on periodic surface gratings

We report on the X-ray Bragg diffraction analysis of periodic surface gratings on (100) GaAs crystals. We show that the X-ray Bragg diffraction is a very powerful method to investigate ultrafine surface gratings and allow us to determine not only the grating period but, in particular, the width of the grooves and to characterize the quality of the sidewalls, which is not easily possible with optical methods. The X-ray diffraction on surface crystal gratings is analogue to the Fraunhofer diffraction of multiple slits or reflection gratings.     

X-ray diffraction diagnostics methods as applied to highly doped semiconductor single crystals

Si(As, P, B) and GaSb(Si) single crystals are used as examples to demonstrate the possibilities of methods of X-ray diffraction for the diagnostics (examination of a real structure) of highly doped semiconductor crystals. Prominence is given to characterizing the state of impurity: whether it is in a solid solution or at a certain stage of its decomposition. An optimum combination of X-ray diffraction methods is found to obtain the most complete information on the microsegregation and structural heterogeneity in crystals with low and high X-ray absorption. This combination is based on X-ray diffraction topography and X-ray diffractometry methods having an increased sensitivity to lattice strains.     

上海光源硬X射线相干衍射成像实验方法初探

相干X射线衍射成像方法是一种先进的成像技术,分辨率可达纳米量级.国际上大多数的同步辐射装置和自由电子激光装置都建立了该成像方法,并有将其作为主要成像技术的趋势.上海光源作为目前国内唯一的一台第三代同步辐射光源,尚未建立基于硬X射线的相干衍射成像实验平台.随着一批以波荡器为光源的光束线站投入使用,使得该方法的建立成为了可能.本文基于上海光源BL19U2生物小角散射线站,通过有效的光路设计,搭建了相干衍射实验平台,在12 keV和13.5 keV能量点均获得了硬X射线相干光束,并基于小孔衍射测量了入射光束的空间相干长度.该平台支持常规和扫描相干衍射实验模式,对小孔衍射图样及波带片扫描衍射图样实现了正确的相位重建,证明了该平台初步具备开展硬X射线相干衍射成像实验的能力.硬X射线相干衍射成像实验平台为国内首次建立,将为国内该实验方法的发展和应用提供有效的软硬件支持.     

半导体超晶格结构参数的X射线衍射运动学理论的计算

本文基于X射线衍射的运动学理论,给出了超晶格的结构因子.运用计算机模拟计算技术,成功地解出了超晶格的结构参数.证明X射线运动学理论适用于所有的超晶格结构,和动力学理论同样有效,而且理论计算简单.     

闪光X射线衍射成像系统设计及实验方法

为实现材料在冲击加载下微观动力学响应测量,基于小型闪光X射线源开展衍射成像系统设计.利用直流X光机及高纯锗探测器实现系统衍射光路的精确调节,克服了闪光X射线瞬时强度高及连续辐射本底强导致的衍射角度确定困难,并采用Scandiflash AB公司TD-450S和成像板建立了衍射成像系统.应用该系统在冲击加载实验中获得了LiF单晶单脉冲的Mo-Kα线静态及动态衍射图像.该闪光X射线衍射系统时间分辨率可达25ns,为冲击压缩实验中材料瞬时结构变化测量提供了新的实验方法.     

Advances in the histopathological characterization of breast tissue using combined X-ray fluorescence and X-ray diffraction data in a multivariate analysis approach

Previous studies have shown that the combination of X-ray fluorescence and X-ray diffraction data can be used as a histopathological characterization tool for breast tissue. Recent advances in energy-dispersive X-ray fluorescence techniques have allowed for benchtop systems to produce useful results in a reasonable time frame, allowing for clinical implementation to be realized. Using a polarized energy-dispersive X-ray fluorescence and energy-dispersive X-ray diffraction system optimized for measuring soft tissues, 38 breast tissue samples (19 normal and 19 diseased) were interrogated. The measured elemental concentrations and adipose and fibrous tissue contents were used in a principal component analysis study to determine the variables that produced the most differentiation between the normal and diseased tissues. For each sample, a soft independent modeling of class analogy technique was utilized to create classification models using the K, Fe, and Zn concentration and adipose and fibrous tissue content of all other breast samples. The class model produced from both X-ray fluorescence and X-ray diffraction data correctly classified 31 of 38 samples with no false positives or false negatives, showing improvement from solely X-ray fluorescence models or X-ray diffraction models alone, and demonstrates the usefulness of such a technique.     

晶体X射线劳厄衍射分束特性研究

本文基于X射线衍射动力学分析了劳厄晶体的分束特性,模拟了晶体吸收和入射光角发散对于透射光和衍射光摇摆曲线的影响,定量给出晶体衍射面内角调节范围和晶体加工厚度对于劳厄衍射分束比的调制.在实验中,采用分析晶体和分束晶体的消色散配置限制入射光角发散的影响,实现300μm厚Si(220)晶体面内角调节劳厄衍射分束的精确测量,并得到300μm, 400μm和500μm厚度Si晶体分束比的调节范围,实现了透射光和衍射光强度的定量调制.     

X-ray optics at the Russian academy of Sciences’ institute of high-purity materials

We examine the current state, prospects for development, and the application of X-ray optics at the IMT-IHPM: X-ray diffraction optics based on X-ray multilayer mirrors and crystals, X-ray acousto-optics based on X-ray diffraction by acoustically modulated crystals, and the application of X-ray methods of diagnostics for the investigation of piezoelectric crystals.     

Crystal growth,structural and photoluminescence studies of L-tyrosine hydrobromide semi organic single crystal

Nearly perfect single crystal of L-tyrosine hydrobromide (LTHB) has been grown at room temperature from the saturated solution prepared from the solvent with optimised normality (2N) using slow evaporation solution growth technique. Crystal system and lattice parameters have been estimated by single crystal X-ray diffraction analysis. Prominent peeks of powder X-ray diffraction pattern have been indexed and diffraction data have been presented. The presence of various functional groups in LTHB has been identified by vibrational and Nuclear Magnetic Resonance spectral study. The crystalline nature and defect during the growth has been studied by obtaining high resolution X-ray diffraction curve (rocking curve) for the title crystal and detailed explanation is given in this paper. Cyclic voltammetric behaviour and photoluminescence properties of LTHB have also been investigated.     

X-ray scattering: A powerful probe of lattice strain in materials with small dimensions

X-ray diffraction was recognized from the early days as highly sensitive to atomic displacements. Indeed structural crystallography has been very successful in locating with great precision the position of atoms within an individual unit cell. In disordered systems, it is the average structure and fluctuations about it that may be determined. In the field of mechanics, diffraction may thus be used to evaluate elastic displacement fields. In this short overview, we give examples from recent work where X-ray diffraction has been used to investigate average strains in lines, films or multilayers. In small objects, the proximity of surfaces or interfaces may create very inhomogeneous displacement fields. X-ray scattering is again one of the best methods to determine such distributions. The need to characterize displacement fields in nano-structures together with the advent of third generation synchrotron radiation sources has generated new and powerful methods (anomalous diffraction, coherent diffraction, micro-diffraction, etc.). We review some of the recent and promising results in the field of strain measurements in small dimensions via X-ray diffraction.     

X-ray diffraction analysis of the surface acoustic wave propagation in langatate crystal

X-ray diffraction on a langatate crystal (La₃Ga_5.5Ta_0.5O₁₄, LGT) modulated by a Λ=12 μm Rayleigh surface acoustic wave (SAW) was studied in a double axis X-ray diffractometer scheme at the BESSY synchrotron radiation source. SAW propagation in the crystal causes sinusoidal modulation of the crystal lattice and the appearance of diffraction satellites on the rocking curves, with their number, angular positions, and intensities depending on the wavelength and amplitude of acoustic vibrations of the crystal lattice. Strong absorption of X-ray radiation in LGT enables the observation of the diffraction spectra extinction at certain SAW amplitudes. X-ray diffraction spectra analysis makes it possible to determine SAW amplitudes and wavelengths, to measure the power flow angles, and investigate the diffraction divergence in acoustic beam in LGT.     

GROWTH OF PREFERENTIALLY ORIENTED CUBIC BORON NITRIDE FILMS BY CHEMICAL VAPOR DEPOSITION

Preferentially oriented cubic boron nitride films on nickel substrates have been grown using hot-filament-assisted rf plasma chemical vapor deposition method. X-ray photoelectron spectroscopy shows that the cubic boron nitride films are stoichiometric. Scanning electron microscopy and X-ray diffraction show that the films are of high quality with well-faceted and (220) preferentially oriented grains, without X-ray diffraction detectable hexagonal boron nitride phase. The nucleation and growth process has been investigated. After 40min deposition, well aligned, well faceted cubic boron nitride nuclei can be seen on the substrnies, and after 2 h deposition, the rectangular grains can be seen on the substrate with their corresponding edges parallel to each other in scanning electron microscopic images. The ratio of the diffraction peak height of (220) face to that of (111) face is about 5.2 in the X-ray diffraction pattern, but the corresponding value of the random cubic boron nitride crystallites is only 0.06.     

X-ray diffraction analysis of C<Subscript>60</Subscript> fullerene powder and fullerene soot

C₆₀ fullerene powder and fullerene soot are examined by the method of small-angle X-ray diffraction. Small-angle diffraction patterns constructed in the Guinier coordinates make it possible to find the radii of inertia of scattering elements. The small-angle diffraction scattering findings agree well with large-angle X-ray diffraction data.     

铌酸钾钠基无铅压电陶瓷的X射线衍射与相变分析

分析了斜方相、四方相铌酸钾钠基无铅压电陶瓷材料的结构和X射线衍射图谱的特点. 对于铌酸钾钠基压电材料斜方相结构, 从构成晶胞的一个单斜原胞进行分析, 计算出X射线衍射谱上每个衍射角附近的衍射峰数目和相对强度. 提出了2θ在20°—60°范围内根据(1 0 2)衍射峰(52°附近)和(1 2 1)衍射峰(57°附近)劈裂的数目区分斜方和四方相的新方法. 对于多晶陶瓷粉末, 可以更简便的由22°(或45°)附近前后峰的相对高低来判断斜方、四方相. 关键词： 铌酸钾钠 无铅压电陶瓷 X射线衍射 相变     

基于光栅衍射的晶体X射线衍射缺级的理论基础和实验研究

以光栅衍射缺级理论为切入点对晶体X射线衍射缺级的现象、产生的根源进行了理论分析,得出：(1) 晶体X射线衍射缺级存在的可能性在于某些晶体材料晶胞的几何结构因子为零;(2) 在复式格子晶体或具有某种特殊缺陷的晶体的X射线衍射图样中存在缺级是这方面实验研究的方向。这些结论在材料物相、材料结构类型和不完整性分析等方面具有一定的参考价值。     

强度关联三维衍射层析的实验研究

提出了一种基于强度关联成像的新型三维衍射层析技术.利用强度关联成像技术(鬼成像)可实现无透镜傅里叶变换的特点,并结合衍射层析技术和二步相位恢复算法,使用波长为650 nm的赝热光实现了强度关联三维衍射层析.详细描述了强度关联三维衍射层析的基本原理以及具体实验结果,为在第三代同步辐射光源实现非相干X光衍射成像积累了经验.