Kossel-Möllenstedt衍射花样特征及薄晶体厚度测定  

Characteristics of Kossel-Möllenstedt diffraction pattern and measurement of thin crystal thickness

作　　者：娄艳芝 LOU Yan-zhi(AECC Beijing Institute of Aeronautical Materials,Beijing 100095,China)

机构地区：[1]中国航发北京航空材料研究院,北京100095

出　　处：《电子显微学报》2021年第3期234-241,共8页Journal of Chinese Electron Microscopy Society

摘　　要：本文利用会聚束电子衍射(CBED)技术测定了晶体Si的局部厚度和消光距离ξ,讨论了关键参数n_(1)取不同值时的数据特点及对分析结果的影响规律,明确了n_(1)的确定方法,总结了Kossel-Möllenstedt(K-M)衍射花样特征及影响因素,给出了Si晶体(400)晶面K-M衍射花样的暗条纹位置预测图。结论如下:当n_(1)<真值时,在数据点较少(≤5)的情况下,数据近似符合直线关系且拟合直线斜率为正;当n_(1)=真值时,拟合直线斜率为负;当n_(1)>真值时,在数据点较少(≤5)的情况下,数据近似符合直线关系且拟合直线斜率为负,数据点较多时,远离衍射盘中心的数据会落在拟合直线的上方;如果n_(1)的取值偏大,会导致消光距离的分析结果偏小,同时试样厚度的分析结果偏大;加速电压的差异会影响K-M花样的衬度;K-M花样暗条纹之间的距离随着距离衍射盘中心距离的增大而逐渐减小;第一暗条纹距衍射盘中心的距离Δθ_(1)和第一暗条纹对应的n_(1)值均与消光距离ξ和试样厚度t有关。In this paper,the silicon crystal thickness and extinction distance are determined by the method of convergent-beam electron diffraction(CBED)at an electron beam energy of 200 kV.Additionally,the order of the first dark line nearest to the center of the diffraction disk n_(1) and its influence on the analysis results is discussed.The extinction distance and thin foil thickness t are analyzed and the determination method of n_(1) value is defined.In addition,the characteristics of K-M patterns are summarized,and the influence of accelerating voltage and sample thickness on K-M patterns is discussed.The results show that if the value of n_(1) is smaller than the true value,the data approximately conforms to the linear relationship and the slope of the fitting line may be positive when the number of data points is less than 5.If n_(1) is equal to the true value,the slope of the fitting line is negative.If the value of n_(1) is larger than the true value,the data approximately conforms to the linear relationship and the slope of the fitting line is negative when the number of data points is less than 5.If the value of n_(1) is larger than the true value,the data points corresponding to the dark line far away from the center of the diffraction disk will be concentrated above the fitting line.This characteristic can be used to determine the value of n_(1).If the value of n_(1) is larger than the true value,the larger the value of n_(1),the smaller the extinction distance and the larger the sample thickness.The value of the accelerating voltage will affect the contrast of the K-M patterns.In a K-M pattern,the distance between adjacent dark lines decreases with the increase of the distance between the dark line and the center of the diffraction disk.The distance between the first dark line and the center of the diffraction disk is related to the extinction distance and the thickness of the sample.Finally,a model for predicting the position of dark lines on K-M patterns of a silicon crystal(400)plane is given at an electr

关 键 词：透射电子显微术 会聚束电子衍射 K-M衍射花样 薄晶体厚度 消光距离 

分 类 号：TB303[一般工业技术—材料科学与工程] TG115.215.3[金属学及工艺—物理冶金]