高分辨电子显微学方法及其在半导体材料研究中的应用

发布时间：2018-01-16 13:02

本文关键词：高分辨电子显微学方法及其在半导体材料研究中的应用　出处：《中国科学院大学(中国科学院物理研究所)》2017年博士论文　论文类型：学位论文

【摘要】：高分辨电子显微学作为从原子尺度评价材料内部结构的最有力的实验手段之一,被广泛应用于各种材料的研究。但是,由于透射电镜成像系统的像差和样品厚度等的影响,高分辨像未必能反映正确的晶体结构信息。为此往往需对高分辨像做细致的像衬分析或使用图像处理方法等来提升图像的分辨率以确定晶体结构。随着球差校正器的出现及广泛使用,电镜分辨率提升至0.1 nm甚至更高,多数情况下可分辨所有原子;并且球差系数的可调节性也为研究人员提供了更多的实验手段。然而,已有的像衬理论已难以对球差校正高分辨像作出很好的解释,因此有必要对球差校正像的像衬理论及相应的图像处理方法进行研究。本论文研究内容可分为两部分:一部分介绍了高分辨电子显微学及像解卷处理方法在Ga N薄膜缺陷结构测定中的应用;另一部分介绍了对球差校正高分辨像中非线性信息的研究工作。具体内容包括:1.由200 kV普通电镜拍摄的分辨率仅为约0.2 nm的高分辨像出发,在原子尺度上测定了Ga N薄膜中多种缺陷的核心结构。首先,利用解卷处理将原本不直接反映待测晶体结构的实验像转变为结构像,或称解卷像,在此过程中使用了衍射振幅校正技术,以减弱动力学效应对像衬的影响,提高解卷像的质量;在解卷像上,间距仅为0.113 nm的Ga-N原子柱不能彼此完全分开,但仍可利用像衬分析技术分辨出这两类原子;之后由解卷像推导出多种缺陷的原子组态,包括层错、不全位错、60°全位错和60°分解位错等,确定了缺陷核心的类型、极性和形成机制等;其中多种位错核心的原子组态为首次由实验像获得。2.结合透射交叉系数(TCC)理论和赝弱相位物体近似(PWPOA)理论对衍射图(即高分辨像强度的傅里叶变换)中包含的非线性信息进行了研究。利用PWPOA理论获得出射波函数的表达式后,结合TCC理论得到了衍射图中线性信息I_1(?)和非线性信息I_2(?)的解析表达式,对其强度和相位与样品厚度和成像条件的关系进行了分析;由于I_1(?)和I_2(?)分别为C_s和Δ1f_(eff)的奇函数和偶函数,据此提出了一种分离球差校正像中线性和非线性信息的方法;并研究了非线性信息对球差校正高分辨像的衍射图及解卷处理产生的影响。
[Abstract]:High resolution electron microscopy (HREM) is one of the most powerful experimental methods to evaluate the internal structure of materials from the atomic scale, and has been widely used in the study of various materials. Due to the aberration of the TEM imaging system and the thickness of the sample. High resolution image may not reflect correct crystal structure information. For this reason, it is necessary to make careful contrast analysis of high resolution image or to use image processing method to improve the resolution of the image to determine the crystal structure. The appearance and wide use of the device. The resolution of electron microscope is increased to 0.1 nm or higher, and in most cases all atoms can be distinguished. Moreover, the adjustable spherical aberration coefficient also provides more experimental means for researchers. However, the existing contrast theory is difficult to explain the spherical aberration correction high resolution image. Therefore, it is necessary to study the contrast theory of spherical aberration correction image and the corresponding image processing methods. In part, the application of high resolution electron microscopy and image deconvolution in the determination of defect structure of gan thin film is introduced. In the other part, the nonlinear information of spherical aberration correction in high resolution image is introduced. The specific contents include: 1. The resolution taken by 200 kV ordinary electron microscope is only about 0.2. High resolution image at nm. The core structures of various defects in gan thin films were measured at atomic scale. Firstly, the experimental images which did not directly reflect the crystal structure were transformed into structural images, or deconvolution images, using deconvolution processing. In order to reduce the influence of dynamic effect on image contrast and improve the quality of deconvolution image, the diffraction amplitude correction technique is used in this process. In unwinding images, the Ga-N atoms with a distance of only 0.113nm can not be separated completely from each other, but the two kinds of atoms can still be distinguished by contrast analysis. Then, the atomic configurations of various defects are deduced from the deconvolution image, including stacking faults, incomplete dislocations, 60 掳total dislocations and 60 掳decomposed dislocations, and the types, polarity and formation mechanism of defect cores are determined. The atomic configurations of many dislocation cores are obtained from experimental images for the first time. The diffraction patterns are obtained by combining the transmission cross coefficient (TCC) theory with the pseudo-weak phase object approximation PWPOA theory. The nonlinear information contained in the Fourier transform of high resolution image intensity is studied. The expression of the emissive wave function is obtained by using the PWPOA theory. Based on the TCC theory, the linear information in the diffraction pattern is obtained. ) and nonlinear information I _ 2s? The relationship between the intensity and phase, the thickness of the sample and the imaging condition is analyzed. ) and I2C? ) the odd function and even function of C _ s and 螖 _ 1F _ T _ f _ f _ f _ f _ f _ f respectively, and a method for separating the midline and nonlinear information of spherical aberration correction image is presented. The influence of nonlinear information on the diffraction pattern and deconvolution of spherical aberration correction high resolution image is studied.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN304

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