高分辨率多晶多反射X射线衍射仪在半导体材料分析中的应用

用高分辨率多晶多反射Ｘ射线衍射仪进行衍射空间的二维扫描是目前非损伤性表生半导体材料质量的手段之一。不同质量的材料在二维衍射空间中的衍射图形状不同。本文以ＧａＡＳ／ＡｌＧａＡｓ为例，展示了如何利用Ｘ射线的二维衍射空间图的形状来定性地分析半导体单晶样品的宏观弯曲，微观倾斜，组分梯度，应变，弛豫以及平行于界面的连续性等问题。     

透射式GaAs光电阴极AlGaAs/GaAs外延层在热应力作用下晶格弯曲的倒易点二维图研究

本文介绍了倒易点及其倒易点二维图的概念、倒易点形状及其倒易点二维图同晶格形变的关系,推导了热应力作用下双层膜发生弯曲的理论公式,阐明了晶格弯曲的原因和晶格倒易点二维图展宽的方向,分析了GaAs光电阴极AlGaAs/GaAs外延层的实测倒易点二维图,最后提出了降低AlGaAs/GaAs外延层中的热应力的技术途径.     

薄膜、多层膜和一维超点阵材料的X射线分析新进展

Ｘ射线散射和衍射对于厚度为几个原子层到几十微米的薄膜材料是灵敏的。一般而言,Ｘ射线方法是非破坏性的,其中不要求样品制备,它们提供恰如其分的技术路线,以获得薄膜材料的结构等信息;分析能对从完整单晶膜和多晶膜到非晶膜的所有材料进行。本文评述了用Ｘ射线方法表征和研究这类薄膜材料的新进展。全文包括引论、常用的Ｘ射线方法、原子尺度薄膜的研究、工程薄膜和多层膜的研究、一维超点阵结构研究、超点阵界面粗糙度的Ｘ射线散射理论、不完整性和应变的衍射空间图或倒易空间图研究七个部分     

Diffuse scattering data acquisition techniques

Techniques are presented for acquiring and reducing X-ray diffuse scattering data from disordered crystalline materials. These methods are part of a comprehensive approach to study disorder in novel quasicrystalline phases as a function of temperature, but can be applied without further adaptation to periodic crystalline systems. By fully exploiting the possibilities of modern two-dimensional X-ray detector systems - using imaging plates or charge coupled devices (CCD) - large volumes of reciprocal space can be measured in a quantitative and rapid way. For this purpose, the classical rotation method for collecting integrated Bragg intensities is extended for acquiring quasi-continuous diffuse diffraction data. A new high-temperature furnace and helium beam path, designed for the diffraction geometry of the rotation method, are integral parts of the diffraction system. New methods are presented for handling the reduction of diffuse diffraction data from area detectors. One of the key techniques is the reconstruction of arbitrary slices and volumes in reciprocal space from a single series of rotation images taken from an arbitrarily oriented single-crystal (reciprocal space mapping).     

透射式GaAs光电阴极AlGaAs/GaAs外延层倒易点二维图分析

本文介绍了摇摆曲线和倒易点二维图在评价晶格完整性时的特点,分析了透射式GaAs光电阴极样品AlGaAs/GaAs外延层的倒易点二维图,获得了晶面弯曲以及AlGaAs外延层中Al组份变化等方面的信息,为优化外延工艺提供了可靠的保证.     

Theory of Diffuse X-Ray Scattering from Surface Blisters

A theory of the diffuse X-ray scattering on randomly distributed surface blisters, which constitute a new type of defects, has been developed. An expression for the amplitude of diffuse X-ray scattering from surface blisters has been obtained within the model of a truncated spherical layer. Scattering intensity distribution maps from surface blisters have been numerically simulated. The effect of the elastic bending of reflecting planes of the lattice of surface blisters on the angular distribution of the scattering intensity in the reciprocal space has been revealed.     

A novel multi‐detection technique for three‐dimensional reciprocal‐space mapping in grazing‐incidence X‐ray diffraction

A new scattering technique in grazing‐incidence X‐ray diffraction geometry is described which enables three‐dimensional mapping of reciprocal space by a single rocking scan of the sample. This is achieved by using a two‐dimensional detector. The new set‐up is discussed in terms of angular resolution and dynamic range of scattered intensity. As an example the diffuse scattering from a strained multilayer of self‐assembled (In,Ga)As quantum dots grown on GaAs substrate is presented.     

The atomic scale structure of saccharose-based carbons

Abstract

Activated carbons (ACs) have a wide range of applications, in which the largely expanded specific surface plays a major role. The question of their structure came back to the limelight with the discovery of nanotubes fullerenes, which suggested that curved surfaces may be present in their structure and which incorporates well into the ideas of ACs porous structure. The source of those curved surfaces is atomic defects present inside the in-plane graphitic honeycomb lattice. Such defects have a crucial influence on the macroscopic morphology as well as physical properties of the material. The activated carbon (AC) in this work was derived from carbonised saccharose by activation with NaOH. Both materials – before and after activation were investigated. The main methods used in this study are wide angle neutron scattering and wide angle X-ray scattering combined with computer simulations. Confirmation of the proposed structures was sought with high-resolution transmission electron microscopy and Raman scattering. In this case, the use of classical crystallography to interpret experimental data was impossible due to the lack of periodic three-dimensional symmetry. Due to this fact, the data was analysed both in real and reciprocal space in the form of a pair correlation function and a structure factor. The experimental data were compared with calculated atomistic models. As a validation, the discrepancy factor between the theoretically and experimentally obtained functions was used. The presented innovative approach can be applied to different carbon materials with varying degrees of disorder.     

Achieving epitaxy between incommensurate materials by quasicrystalline interlayers

Epitaxial interfaces of commensurate periodic materials can be characterized by a locking into registry of their atomic structure. This characteristic is identified as a natural framework to capture the essence of epitaxy also for systems including quasicrystalline materials. The resulting general definition for epitaxy requires a matching of reciprocal lattice points. The consequences for the real space structure of an epitaxial interface between quasiperiodic and periodic materials are explored and an experimental realization of such an interface is presented. It is demonstrated that due to their higher number of reciprocal lattice basis vectors (exceeding three), quasicrystals can provide interlayers epitaxially linking incommensurate materials.     

Spin-liquid correlations in the Nd-langasite anisotropic kagomé antiferromagnet

Dynamical magnetic correlations in the geometrically frustrated Nd(3)Ga(5)SiO(14) compound were probed by inelastic neutron scattering on a single crystal. A scattering signal with a ring shape distribution in reciprocal space and unprecedented dispersive features was discovered. Comparison with calculated static magnetic scattering from models of correlated spins suggests that the observed phase is a spin liquid inherent to an antiferromagnetic kagomé-like lattice of anisotropic Nd moments.     

High-resolution X-ray diffraction analysis of SnTe/Sn1−xEuxTe superlattices grown on (1 1 1) BaF2 substrates

A set of SnTe/Sn_1−xEu_xTe superlattice (SL) samples with increasing nominal Eu content x up to 0.28 was successfully grown on (1 1 1) BaF₂ substrates by molecular beam epitaxy. A complete structural characterization was performed by triple-axis X-ray diffractometry and reciprocal space mapping. The X-ray results showed that, despite the phase separation that normally occurs for unstrained Sn_1−xEu_xTe layers with x0.02, an SL stack with homogeneous individual layers can be formed for SL samples with a nominal Eu content up to 0.16. No SL satellite peak structure could be identified for samples with x values higher than 0.24. The structural parameters of the individual layers that compose the SL were determined using a best-fit simulation procedure which compared the calculated X-ray spectra to the measured (2 2 2) ω/2Θ scans. The strain information used in the simulation was obtained from the reciprocal space maps measured around the (2 2 4) lattice point.     

透射式GaAs光电阴极的X射线衍射研究

本文介绍了高精度多晶多反射X射线衍射仪的一种新的应用.首次将其应用于研究高灵敏度第三代微光象增强器中由掺Zn的p型GaAs/GaAlAs、玻璃组成的光电阴极的材料特性；发展了用倒格子空间衍射图方法评价光电阴级组件晶体质量的方法.通过分析得知,衍射强度在倒格子空间沿。方向展宽主要起因于晶体中的嵌镶效应的增强.文中采用衍射动力学理论的计算方法并忽略初始条件,模拟后得到的曲线与衍射强度沿ω/θ方向的投影强度曲线符合的比较好.粘接良好的阴极样品表明,GaAs/GaAlAs晶格常数的变化基本上可以消除,但粘接引起的嵌镶效应的增强却不能完全消除.     

透射式GaAs光电阴极AlGaAs窗层和GaAs光电发射层界面应变状况的X射线衍射研究

本文介绍了应变和弛豫的概念以及倒易点在倒易空间的分布,阐明了GaAs光电阴极AlGaAs窗层和GaAs光电发射层界面应变状况的X射线衍射的分析方法,最后给出了实例.     

Corelli: Efficient single crystal diffraction with elastic discrimination

Single crystal diffuse scattering provides one of the most powerful probes of short-range correlations on the 1–100 nm scale, which often are responsible for the extreme field response of many emerging phenomena of great interest. Accurate modeling of such complex disorder from diffuse scattering data however puts stringent experimental demands, requiring measurements over large volumes of reciprocal space with sufficient momentum and energy resolution. Here, we discuss the potential of the cross-correlation technique for efficient measurement of single crystal diffuse scattering with energy discrimination, as will be implemented in a novel instrument, Corelli. Utilizing full experiment simulations, we show that this technique readily leads up to a fifty-fold gain in efficiency, as compared to traditional methods, for measuring single crystal diffuse scattering over volumes of reciprocal space with elastic discrimination.      

X-ray critical scattering in BaTiO3

Critical scattering of X-rays in a BaTiO₃ monocrystal was measured around the [005] reciprocal lattice point. The constant intensity curves in reciprocal lattice space are exactly analogous with those determined by Yamada et al. around the [200] point.     

Monofunctional gold nanoparticles: synthesis and applications

The ability to control the assembly of nanoparticle building blocks is critically important for the development of new materials and devices. The properties and functions of nanomaterials are not only dependent on the size and properties of individual particles, but also the interparticle distance and interactions. In order to control the structures of nanoassemblies, it is important to first achieve a precise control on the chemical functionality of nanoparticle building blocks. This review discusses three methods that have been reported recently for the preparation of monofunctional gold nanoparticles, i.e., nanoparticles with a single chemical functional group attached to each particle. The advantages and disadvantages of the three methods are discussed and compared. With a single functional group attached to the surface, one can treat such nanoparticles as molecular building blocks to react with other molecules or nanoparticles. In other words, by using appropriate chemical reactions, nanoparticles can be linked together into nanoassemblies and materials by covalent bonds, similar to the total chemical synthesis of complicated organic compounds from smaller molecular units. An example of using this approach for the synthesis of nanoparticle/polymer hybrid materials with optical limiting properties is presented. Other potential applications and advantages of covalent bond-based nanoarchitectures vs. non-covalent interaction-based supramolecular self-assemblies are also discussed briefly in this review.     

X-ray equipment for laboratory and synchrotron studies of thin-film crystalline structures

The capabilities of X-ray equipment produced by Radicon Ltd. for the high-resolution structural investigation of single crystals and thin films using different methods including high-resolution methods, are demonstrated. A double-crystal DSO-1T X-ray diffractometer with a large sample-to-detector distance and a narrow slit in front of the detector allows one to perform high-quality mapping of the GaAs/GaP/Si heteroepitaxial structure in reciprocal space. A new double-crystal PDP console for the DRON-3 diffractometer provides the mapping of large wafers through the use of rocking curves. A new specialized X-ray DSO-2-01 diffractometer equipped with a motorized console for linear displacement of detector and rotary slit changer in front of the detector ensures automatic crystal orientation and precise measurements of the crystal lattice. All X-ray diffractometers manufactured by Radicon have rather flexible software including a custom macros editor.     

Multicrystal X-ray diffraction of heteroepitaxial structures

An appraisal of high-resolution multi-crystal multi-reflection diffractometry (HRMCMRD) and topography is presented to illustrate its potential for structure analysis. Examples of methods for extracting lateral interface roughness, studying layered structures with imperfect epitaxy (including strained layer structures) are given to show the wealth of information available from X-ray techniques. The advantages of diffraction space mapping are discussed in addition to the use of topography to interpret the diffuse and Bragg scattering. The HRMCMRD has a dynamic range of 10⁶ and can record topographs with intensities less than 1 count/s.     

Study on the lattice distortion of the As-prepared nanosized TiO2 particles via detonation method

Quantitative XRD measurements of the nanosized TiO₂ particles obtained from the detonation soot have been carried out. The lattice parameters, such as grain size, cell volume, lattice constants and lattice strain were obtained. The relationships between the change ratio of cell volume (the reciprocal of the particles size, or the mass ratio of explosive and TiO₂ precursor) and the lattice strain of the different TiO₂ phases were also discussed. The relationship between the change ratio of cell volume and the particle size of TiO₂ particles was also studied. The results demonstrated that with the decreasing of the particles size, the lattice strain of anatase phase increased, while the lattice strain of rutile phase increased firstly and then decreased to some extent. It is different from the linear relationship between the lattice distortion and the reciprocal of the particles size reported in other literatures. In the meantime, the lattice strains were different with the different mass contents of RDX in the microstructures of the TiO₂ particles. The direct reflection of microstructure changes is the changes of the particle size of TiO₂ particles. Based on the XRD results, the particular characteristics of the detonation process and interfacial effects of nanocrystalline materials, a crude explanation was also given.