氧化铬外延薄膜的x射线研究

采用分子束外延技术(MBE)在MgO(001)基板上沉积了氧化铬薄膜，并利用x射线衍射 (XRD)和x射线反射谱(XRR)对薄膜的晶体结构进行了表征.θ—2θ扫描和倒易空间图(R SM)揭示出薄膜为单相c轴外延生长，晶体结构为体心正交，晶胞常数a，b，c分别为0.8940±0.0003，0.298±0.0002和0.3897±0.0002nm.扫描表明薄膜在面内具有90°孪晶，取向关系为a∥MgO〈110〉,c∥MgO(001).XRR谱测得薄膜的电子 密度为1350±20nm-3，与由晶胞体积 计算得 关键词： 一氧化铬薄膜 x射线衍射 倒易空间图 x射线反射谱     

Residual stress/strain analysis in thin films by X-ray diffraction

Residual stresses are found in the majority of multilayer thin film structures used in modem technology. The measurement and modeling of such stress fields and the elucidation of their effects on structural reliability and device operation have been a “growth area” in the literature, with contributions from authors in various scientific and engineering disciplines.

In this article the measurement of the residual stresses in thin film structures with X-ray diffraction techniques is reviewed and the interpretation of such data and their relationship to mechanical reliability concerns are discussed.     

Structural investigation of thin tetracene films on flexible substrate by synchrotron X-ray diffraction

Structural properties of tetracene thin films grown by vacuum sublimation on a flexible Mylar^© substrate have been investigated by means of synchrotron X-ray diffraction. The films are polycrystalline and are made up of crystalline domains oriented with the (0 0 l) planes almost parallel to the substrate and completely misoriented around the surface normal. Two crystallographic phases (α and β thin film phases) have been identified. They differ for the d_h k l interplanar spacing, both larger than that of the bulk. As a comparison, results from tetracene films grown on SiO₂ have been reported to investigate the different charge transport properties of films grown on Mylar and on SiO₂ substrates.     

Evaluation of both composition and strain distributions in InGaN epitaxial film using x-ray diffraction techniques

The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction (XRD) techniques, including out-of-plane XRD at special planes, in-plane grazing incidence XRD, and reciprocal space mapping (RSM). It is confirmed that the measurement of (204) reflection allows a rapid access to estimate the composition without considering the influence of biaxial strain. The two-dimensional RSM checks composition and degree of strain relaxation jointly, revealing an inhomogeneous strain distribution profile along the growth direction. As the film thickness increases from 100 nm to 450 nm, the strain status of InGaN films gradually transfers from almost fully strained to fully relaxed state and then more In atoms incorporate into the film, while the near-interface region of InGaN films remains pseudomorphic to GaN.     

基于X射线衍射的GaN薄膜厚度的精确测量

结合Williamson-Hall plot方法和线型分析方法的优点,提出了一种有效分离有限晶粒尺寸和非均匀应力等X射线衍射展宽效应的方法,可以用于GaN外延层厚度等参数的快速精确测量.用该方法对一系列在蓝宝石衬底上生长的厚度在0.7—4.2μm的GaN外延膜进行了测量,并与椭圆偏振光谱法测量结果进行了比较,结果表明其差别<4%,反应了这种方法的准确性. 关键词： GaN薄膜 厚度测量 X射线衍射     

Be薄膜应力的X射线掠入射侧倾法分析

由于铍薄膜极易被X射线穿透, 传统的几何模式下很难获得有效的X射线衍射应力分析结果. 本文采用掠入射侧倾法分析SiO₂基底上Be薄膜残余应力, 相比其他衍射几何方法, 提高了衍射的信噪比, 获得的薄膜应力拟合曲线线形较好. 对Be薄膜的不同晶面分析, 残余应力结果相同, 表明其力学性质各向同性; 利用不同掠入射角下X射线的穿透深度不同, 获得应力在深度方向上的分布; 由薄膜面内不同方向的残余应力相同, 确定薄膜处于等双轴应力状态. 关键词： Be薄膜 X射线衍射 应力     

High pressure X-ray diffraction study of CaMnO3 perovskite

Using a diamond anvil cell device and synchrotron radiation,the in-situ high-pressure structure of CaMnO3 has been investigated.In the pressure up to 36.5 GPa,no pressure-induced phase transition is observed.The pressure dependence on the lattice parameters of CaMnO3 is reported,and the relationship of the axial compression coefficients is βa 〉 βc 〉 βb.The isothermal bulk modulus K298=224（25） GPa is also obtained by fitting the pressure-volume data using the Murnaghan equation of state.     

X-ray analysis of ZnO nanorods grown by microwave irradiation heating on ZnO films

Utilizing microwave irradiation heating, 100-nm-diameter ZnO nanorods were grown from aqueous solution on sputtered ZnO films on glass substrates. Its out-of-plane X-ray diffraction (XRD) measurement indicated that the ZnO nanorods were grown with c-axis orientation, similar with the underlying ZnO films. In the in-plane XRD measurement, intensity of the () diffraction was comparable with that of the () one, suggesting their intensity ratio would contain useful information on nanorods density.     

High pressure X-ray diffraction study of SrMnO3 perovskite

Using a diamond anvil cell device and synchrotron radiation, the in-situ high-pressure structure of SrMnO3 has been investigated. At pressure up to 28.6 GPa, no pressure-induced phase transition is observed. The lattice parameters as a function of pressure is reported, and the relationship of the axial compression coefficients is β<,a>> β<,c>. The isothermal bulk modulus K<,298>=266(4) GPa is also obtained by fitting the pressure- volume data using the Murnaghan equation of state.     

High pressure X-ray diffraction study of CaMnO3 perovskite

Using a diamond anvil cell device and synchrotron radiation,the in-situ high-pressure structure of CaMnO3 has been investigated.In the pressure up to 36.5 GPa,no pressure-induced phase transition is observed.The pressure dependence on the lattice parameters of CaMnO3 is reported,and the relationship of the axial compression coefficients is βa >βc > βb.The isothermal bulk modulus K298=224(25)GPa is also obtained by fitting the pressure-volume data using the Murnaghan equation of state.     

High pressure X-ray diffraction study of SrMnO3 perovskite

Using a diamond anvil cell device and synchrotron radiation, the in-situ high-pressure structure of SrMnO₃ has been investigated. At pressure up to 28.6 GPa, no pressure-induced phase transition is observed. The lattice parameters as a function of pressure is reported, and the relationship of the axial compression coefficients is β_a>β_c. The isothermal bulk modulus K₂₉₈=266(4) GPa is also obtained by fitting the pressure-volume data using the Murnaghan equation of state.     

Structural and optical properties of La-doped BaSnO3 thin films grown by PLD

In this study the structural and optical properties of lanthanum-doped BaSnO₃ powder samples and thin films deposited on fused silica were investigaed using laser ablation. Under an oxygen pressure of 5×10⁻⁴ mbar, phase pure BaSnO₃ films with a lattice constant of 0.417 nm and grain size of 21 nm were prepared at 630 °C. The band gap of BaSnO3 powder sample and thin films was calculated to be 3.36 eV and 3.67 eV, respectively. There was a progressive increase in conductivity for thin films of BaSnO₃ doped with 0~7 at% of La. The highest conductivity, 9 Scm⁻¹, was obtained for 7 at% La-doped BaSnO₃. Carrier concentration, obtained from Burstein-Moss (B-M) shift, nearly matches the measured values except for 3 at% and 10 at% La-doped BaSnO₃ thin films.     

X射线衍射进展简介

100年前,劳厄等证明X射线对硫酸铜晶体具有衍射能力,揭开了X射线衍射分析晶体结构的序幕.100年的发展,X射线衍射已经成为自然科学乃至医学、考古、历史学等众多学科发展的必备技术.文章介绍了X射线衍射现象的发现历史,X射线运动学和动力学理论的发展概况,并举例说明了X射线衍射在粉末多晶体、单晶体和人工功能晶体以及人工薄膜材料中的具体应用情况,最后简要展望了X射线衍射技术的发展前景.     

Thickness measurement of GaN epilayer using high resolution X-ray diffraction technique

In this paper we propose a new method for measuring the thickness of the GaN epilayer, by using the ratio of the integrated intensity of the GaN epilayer X-ray diffraction peaks to that of the sapphire substrate ones. This ratio shows a linear dependence on the GaN epilayer thickness up to 2 μm. The new method is more accurate and convenient than those of using the relationship between the integrated intensity of GaN epilayer diffraction peaks and the GaN thickness. Besides, it can eliminate the absorption effect of the GaN epilayer.     

Structural,luminescent, and morphological properties of Eu3+-doped NaTaO3 thin films grown by magnetron sputtering

Radio-frequency (RF)-sputtered Eu³⁺-doped NaTaO₃ thin films were grown at different deposition temperatures. The X-ray diffraction patterns revealed that all thin films contained two mixed phases of NaTaO₃ and Na₂Ta₈O₂₁. The photoluminescence spectra of the thin films consisted of a strong orange emission (592 nm) and two weak red bands (616 nm and 689 nm), suggesting that more Eu³⁺ ions in the NaTaO₃ host crystal were located at inversion symmetry sites. The maximum intensities of all emission peaks were achieved for the sample grown at 100 °C, in which the gravel-shaped crystallites evolved with a band gap energy of 4.61 eV, chromaticity coordinates of (0.554, 0.434), and average transmittance of 92.4%. These results indicate that the photoluminescence intensity, band gap energy, and color tunability can be achieved for RF-sputtered Eu³⁺-doped NaTaO₃ thin films by varying the growth temperature.     

利用高分辨X射线衍射研究磷酸二氢钾晶体晶格应变应力

采用高分辨X射线衍射技术对大尺寸磷酸二氢钾(KDP)晶体的晶格应变进行了测量,并定量分析了其晶格应力.探讨出KDP晶体容易沿着[001]方向发生开裂,与实际工作中的开裂现象相符合;进一步归纳总结了晶体生长过程中引入内应力而导致晶体开裂的主要因素.研究结果为提出相应的晶体防裂措施提供了重要的理论基础.     

Reciprocal space mapping

This review covers the recent advances in reciprocal space mapping. The experimental techniques as well as the theoretical and conceptual developments are discussed. The advantages of reciprocal space mapping over the conventional single scan X-ray scattering methods become clear from the examples presented. Extracting the additional information from mapping in reciprocal space maps has led to a deeper understanding of materials. Imperfect materials benefit enormously from these methods. Near perfect materials also indicate weak diffuse scattering that can now be interpreted in terms of defects, etc., whereas with single scans the influence is difficult to observe and separate from other features. Reciprocal space maps can be collected with both high and low angular resolution diffractometers, depending on the application, although a combination of resolutions may be necessary. It is also growing in importance in the analysis of materials using specular reflectometry. High-resolution reciprocal space mapping is not restricted to good crystalline quality. Examples of reciprocal space mapping are given for semiconductors, metals, ceramics and biological samples. For semiconductor materials, reciprocal space mapping has now become almost routine in the study of lattice relaxation in thin layers and in the assessment of the “quality” of materials. Combinations of mapping with topography and precision lattice parameter determination are also discussed. The latter part of this review discusses the advantages of three-dimensional reciprocal space mapping, which takes the analysis further. With this method the full three-dimensional shapes in reciprocal space can be studied.     

High resolution X-ray diffraction studies at high pressures

Abstract

The principal sources of systematic error in high-pressure x-ray structure determination with a diamond anvil cell have been studied in detail. The results of these studies have been used to develop techniques to minimise or correct for these effects.