透射式GaAs光电阴极AlGaAs/GaAs外延层X射线衍射摇摆曲线半峰宽研究

本文研究了晶体X射线摇摆曲线半峰宽同其晶格完整性之间的关系,外延层之间X射线衍射的非相干叠加以及热应力引起的晶格应变和晶面弯曲对摇摆曲线半峰宽宽窄的影响.     

X射线双晶衍射摇摆曲线本征半峰宽的理论计算

本文应用X射线衍射动力学理论,推导出Bragg衍射几何X射线双晶衍射反射率的数学表达式。多种晶体、不同衍射的摇摆曲线计算结果表明,σ偏振的摇摆曲线的峰值和积分强度均比π偏振的高。而且半峰宽较宽。同时指出,对圆偏振X射线入射或者A,B两晶体不同类或者两者的衍射级数不相同时,很多文献给出的双晶衍射摇摆曲线半峰宽的近似表达式2^1/2∞不再适用。 关键词：     

半导体应变超晶格结构与界面的X射线双晶衍射研究

本文应用X射线在畸变晶体中的动力学衍射理论,分析了超晶格衍射峰强度分布的规律,计算了应变超晶格中界面变化,层厚波动对双晶摇摆曲线的影响,并初步探讨了超晶格衍射峰之间的小峰消失以及衍射峰宽化的原因,研究表明,衍射峰强度分布依赖于超晶格周期中层厚、成份及应变的综合效果,界面和层厚波动将对摇摆曲线产生一定影响,而晶格弯曲是使衍射峰宽化的主要原因。     

发光多孔硅表面微结构及其晶格畸变的实验研究

用电化学方法制备了不发光多孔硅和发光多孔硅,用X射线双晶衍射对两类多孔硅表面进行了微结构分析和晶体质量表征,实验表明两类多孔硅的微结构间存在着很大差别。不发光多孔硅表面对X射线的双晶衍射摇摆曲线可解叠成两个峰,它们分别来自样品多孔层和单晶硅衬底,而发光多孔硅对X射线的双晶衍射摇摆曲线呈高斯对称分布,不可解叠。发光多孔硅比不发光多孔硅表面晶体质量差,且电化学腐蚀越严重,表面晶体质量下降也越严重。     

透射式GaAs光电阴极AlGaAs/GaAs外延层X射线衍射摇摆曲线研究

利用透射式GaAs光电阴极AlGaAs/GaAs外延层的结构特点及其X射线衍射摇摆曲线分析方法,解释了AlGaAs/GaAs外延层摇摆曲线半峰宽和其衍射角角位移随外延层生长温度升高而增大的现象.     

HgCdTe组分不均性对X射线反射率的影响

本征反射率是X射线衍射摇摆曲线计算机模拟的基础。用X射线动力学理论研究了组分不均匀对HgCdTe材料X射线反射率的影响。研究结果表明,横向组分不均匀性直接影响摇摆曲线的峰形,峰值反射率和半峰全宽随组分不均匀的增大而分别减小和增大,且与组分不均匀性的均方差近似成指数关系,但其积分反射率却基本保持不变;采用多层模型对具有线性组分梯度的HgCdTe半导体材料反射率的计算结果则表明,纵向组分梯度除导致反射率峰值强度下降外,还会引起摇摆曲线产生单边干涉效应,摇摆曲线的半峰全宽和干涉峰间距随组分梯度的增加而增大,而干涉峰间距与干涉周期之间的关系则随组分梯度的增加其偏离线性的程度增大。     

Hg1-xCdxTe/Cd1-zZnzTe的X射线反射率及半峰全宽的动力学研究

X射线衍射摇摆曲线的计算机模拟是一种获得材料晶体质量参量的有效方法，其中材料本征摇摆曲线的计算是计算机模拟的基础。用X射线动力学理论计算了Hg1-xCdxTe和Cd1-zZnzTe本征反射率曲线，并研究了组分、膜厚分别对本征反射率和半峰全宽的影响。结果表明Hg1-xCdxTe和Cd1-zZnzTe的本征反射率和半峰全宽与材料组分和厚度有明显的依赖关系，且该依赖关系取决于X射线在材料中的散射和吸收的相对强弱。薄膜的厚度也是直接影响本征摇摆曲线峰形、半峰全宽和反射率的重要因素，当薄膜厚度小于穿透深度时，表征本征反射率曲线的各个参量均与薄膜厚度有直接的关系。对于(333)衍射面，碲镉汞材料厚度大于7μm后，本征反射率和半峰全宽将不再发生明显变化。     

晶面偏角对利用Voigt函数法计算硅单晶本征晶格应变的影响

研究并制备了不同晶面偏角的Si(111)单晶,经过研磨和抛光使表面粗糙度低至3.4?达到超光滑水平,消除了表面和亚表面损伤层以及其所产生的应力变化.利用高精度X射线衍射仪分别测定了在不同晶面偏角条件下衍射曲线的半高全宽和积分宽度.应用Voigt函数法分析计算了微观应变,通过理论计算和实验对比可知,Si(111)单晶在晶面偏角达到0.749o时,偏角本身所带来的衍射峰半高全宽变化使计算出的应变值误差大于5%.研究结果为其他晶体类似研究提供了重要参考.     

薄膜界面粗糙对双晶摇摆曲线的影响

用X射线衍射动力学理论,模拟计算InP衬底上InGaAs/AllnAs超晶格和InGaAs单层膜的X射线双晶摇摆曲线,计算结果表明:薄膜界面粗糙对单层膜的衍射峰和超晶格的零级衍射峰影响较小,但却明显影响单层膜衍射干涉条纹和超晶格的±1级卫星峰,随着平均界面粗糙度的增大,单层膜衍射干涉条纹强度减弱并趋于消失;超晶格的±1级卫星峰变弱并逐渐展宽,理论计算的模拟双晶摇摆曲线与超晶格实验曲线比较表明:高质量匹配In_0.53Ga_0.47As(85?)/Al_{0.4 关键词：}     

金属有机物化学气相沉积同质外延GaN薄膜表面形貌的改善

为了获得高质量的GaN薄膜材料,研究了金属有机物气相沉积系统中GaN插入层对GaN衬底同质外延层表面宏观缺陷和晶体质量的影响.研究发现,插入层生长温度是影响GaN同质外延膜表面形貌和晶体质量的关键因素.由于生长模式与插入层生长温度相关,随着插入层生长温度的降低,外延膜生长模式由准台阶流模式转变为层状模式,GaN同质外延膜表面丘壑状宏观缺陷逐渐减少,但微观位错密度逐渐增大.通过对插入层温度和厚度的优化,进一步调控外延层的生长模式,最终有效降低了外延层表面的宏观缺陷,获得了表面原子级光滑平整、位错密度极低的GaN同质外延膜,其X射线衍射摇摆曲线(002),(102)晶面半峰宽分别为125arcsec和85arcsec,表面粗糙度均方根大小为0.23nm.     

Rocking Curves of X-ray Asymmetrical Laue Diffraction with Two-Dimensional Curvature of Wave Front

X-ray asymmetrical Laue diffraction in a perfect crystal with plane front surface was considered taking into account the two-dimensional curvature of a wave incident on the crystal. Using an appropriate Green function the dependences of rocking curves on deviation angles from selected exact Bragg direction were examined in the diffraction plane and in the direction perpendicular to the diffraction plane in locally plane wave approximation. The dependence of rocking curves on the degree of asymmetry of diffraction geometry was investigated. Analytical expressions for half widths of rocking curves in the diffraction plane and in the direction perpendicular to the diffraction plane are obtained. Some requirements to spatial and temporal coherence are estimated.     

Rocking Curves of X-Ray Asymmetric Bragg Diffraction with Two-Dimensional Curvature of Wave Front

The X-ray asymmetric Bragg diffraction in a perfect semi-infinite crystal with plane entrance surface is considered taking into account the two-dimensional curvature of the wave front of an incident wave. An expression for reflection coefficient using the Green function is obtained in the approximation of locally plane wave and the rocking curves are investigated as functions of angular departure from the selected exact Bragg direction in the diffraction plane and in the direction perpendicular to the diffraction plane. The shape, position and dimensions of total reflection region of rocking curves are studied depending on the degree of asymmetry of diffraction geometry. The requirements to the spatial and temporal coherence for obtaining the rocking curves are estimated.     

X-ray Laue diffraction with allowance for two-dimensional curvature of the wavefront: The concept a locally plane wave

Symmetrical Laue diffraction in a perfect crystal with a plane entance surface is considered. The two dimensional curvature of the wave front of the incident beam is taken into account. Using the corresponding Green function, a general expression for the amplitude of diffracted wave in the crystal is presented. Based on this expression, the concept of a locally plane wave is analyzed taking into account two-dimensional curvature of the wave front. This concept is used for obtaining the rocking curves depending on the angles of deviation from the chosen exact Bragg direction in both the diffraction plane and in perpendicular direction. The obtained result is compared with the result of the standard dynamical diffraction theory.     

初始化生长条件对a-GaN中应变的影响

利用高分辨X射线衍射(HRXRD)与拉曼散射光谱(Raman scattering spectra)研究了氮化处理与低温AlN缓冲层对低压金属有机化学气相沉积(LP-MOCVD)在r面蓝宝石衬底上外延的a面GaN薄膜中的残余应变的影响。实验结果表明:与氮化处理后生长的a-GaN相比,使用低温AlN缓冲层后生长的a-GaN具有较小的摇摆曲线的半高宽和较低的残余应变,而且其结构各向异性和残余应变各向异性也均有一定程度的降低。因此,与氮化处理相比,低温AlN缓冲层更有利于a-GaN的生长。     

Effects of sapphire substrates surface treatment on the ZnO thin films grown by magnetron sputtering

The surface treatment effects of sapphire substrate on the ZnO thin films grown by magnetron sputtering were studied. The sapphire substrates properties have been investigated by means of atomic force microscopy (AFM) and X-ray diffraction rocking curves (XRCs). The results show that sapphire substrate surfaces have the best quality by CMP with subsequent chemical etching. The surface treatment effects of sapphire substrate on the ZnO thin films were examined by X-ray diffraction (XRD) and photoluminescence (PL) measurements. Results show that the intensity of (0 0 2) diffraction peak of ZnO thin films on sapphire substrates treated by CMP with subsequent chemical etching was strongest, FWHM of (0 0 2) diffraction peak is the narrowest and the intensity of UV peak of PL spectrum is strongest, indicating surface treatment on sapphire substrate preparation may improve ZnO thin films crystal quality and photoluminescent property.     

Effects of AlN nucleation layer thickness on crystal quality of AlN grown by plasma-assisted molecular beam epitaxy

In this paper,the effects of thickness of AlN nucleation layer grown at high temperature on AlN epi-layer crystalline quality are investigated.Crack-free AlN samples with various nucleation thicknesses are grown on sapphire substrates by plasma-assisted molecular beam epitaxy.The AlN crystalline quality is analysed by transmission electron microscope and x-ray diffraction (XRD) rocking curves in both (002) and (102) planes.The surface profiles of nucleation layer with different thicknesses after in-situ annealing are also analysed by atomic force microscope.A critical nucleation thickness for realising high quality AlN films is found.When the nucleation thickness is above a certain value,the (102) XRD full width at half maximum (FWHM) of AlN bulk increases with nucleation thickness increasing,whereas the (002) XRD FWHM shows an opposite trend.These phenomena can be attributed to the characteristics of nucleation islands and the evolution of crystal grains during AlN main layer growth.