XAFS应用于半导体材料研究及分析方法创新

发布时间：2018-05-24 20:44

本文选题：X射线精细结构谱学 + (XAFS)　；参考：《广西大学》2017年硕士论文

【摘要】：本文着重介绍同步辐射这项表征手段的分支技术——X射线精细结构谱学(X-ray absorption fine structure,XAFS),较为全面的介绍了这项技术的原理和应用。全文从XAFS探测半导体材料微观结构的原理、XAFS的实验设备及技术、X射线精细结构谱传统分析手段的介绍与优劣势分析、新方法的创新逐步深入分析这项实用的表征手段。本文的重点在于X射线精细结构谱传统分析手段的介绍与优劣势分析。从1971年开始,XAFS理论分析与数据处理才逐渐被科学的论证和使用。目前,XAFS经历了 40多年的发展并日渐成熟,在该领域传统方法被广泛学习和使用。同时也不乏该领域的研究人员在进行理论研究和数据处理方法创新。作者将传统分析手段应用于半导体材料(6H-SiC 041,050,054,177;AlGaN 401,402,403)中,分析了这两个系列样品的结构特性。由于传统方法需要进行反复的傅里叶变换和拟合,以至于需要花费大量时间调试才能得到一个好的结果。最为重要的是,当样品的结构复杂或者实验数据使用傅里叶变换无法很好的分立壳层时,这些情况下无法用已有的结构模型去拟合。因此,为了解决这个问题,课题组合作导师许谷院士(加拿大麦克马斯特大学教授,加拿大工程院院士)提出了一个新方法[1],用于弥补传统方法的缺陷和短板。新方法从X射线精细结构谱震荡基本原理公式出发,抓住震荡谱形在取某些km值时,使得等式右边为零的特点[1],将拟合整条曲线进而得到未知参数的问题,转变为解N个方程组的问题。通过逻辑推导和分析论证,在求得实验谱波矢空间的震荡零点以及中心原子和散射原子的相位后,利用Matlab求最小值的算法,可以非常容易的找到使用者需要的参数。如中心原子的第一壳层、第二壳层的键长,配位数等。这样,使用者可以非常简便的得到需要的重要结构参数,而不再需要反复的傅里叶变换和拟合。新方法的理论推导完成后,首先运用在Matthew Newville于2004发表的FeO材料上使用[2],发现结果非常可信。进而推广到已有的实验数据上(6H-SiC 041,050,054,177,AlGaN 401,402,403),分析结果与反复拟合得到的结果非常相近。虽然本文对于介绍的新方法提供了较为严密的逻辑推导并初步确定了操作流程,但是仍然还有很多问题需要继续研究和解决,如求rm内部参数的细化,结构扩张到第三层、第四层甚至更外层等问题。在逐步完善这些理论和方法后,本文介绍的方法将可以适用于更广泛的材料领域。
[Abstract]:In this paper, the branch technique of synchrotron radiation (synchrotron radiation), X-ray absorption fine structure, X-ray fine structure spectroscopy, and its principle and application are introduced in detail. Based on the principle of detecting the microstructure of semiconductor materials by XAFS, this paper introduces the experimental equipment and technology of XAFS and analyzes the advantages and disadvantages of the traditional analysis methods of X-ray fine structure spectrum. The innovation of the new method is used to analyze this practical characterization method step by step. The emphasis of this paper is on the introduction and advantage and disadvantage analysis of X-ray fine structure spectrum. Since 1971, XAFS theory analysis and data processing have been scientifically demonstrated and used. XAFS has been developed for more than 40 years, and has been widely studied and used in this field. At the same time, there are many researchers in the field of theoretical research and data processing methods innovation. The author applied the traditional analytical method to the semiconductor material 6H-SiC 041050054177AlGaN 401402403) and analyzed the structural properties of the two series samples. Because the traditional method needs repeated Fourier transform and fitting, it takes a lot of time to debug to get a good result. The most important thing is that when the structure of the sample is complex or the experimental data can not be well separated by Fourier transform, the existing structural model can not be used to fit these cases. Therefore, in order to solve this problem, a new method [1] was proposed by our co-mentor, Academician Xu Gu (Professor McMaster University, Canadian Academy of Engineering), to make up for the defects and shortcomings of traditional methods. Based on the basic principle formula of X-ray fine structure spectral oscillation, the new method holds the characteristic that the oscillatory spectral form is zero to the right of the equation when some km values are taken, and the unknown parameters can be obtained by fitting the whole curve. The problem of solving N equations. Through logical derivation and analysis, after finding the oscillatory zero point in the spectrum vector space and the phase of the center atom and the scattering atom, the parameters needed by the user can be easily found by using the algorithm of Matlab to calculate the minimum value. For example, the first shell of the central atom, the bond length of the second shell, the coordination number, etc. In this way, the user can easily get the important structural parameters without the need of repeated Fourier transform and fitting. After the theoretical derivation of the new method is completed, the method is first applied to the FeO material published by Matthew Newville in 2004, and the results are very reliable. It is further extended to the experimental data of 6H-SiC 041050054177AlGaN 4014024030.The analytical results are very close to those obtained by repeated fitting. Although the new method presented in this paper provides a more rigorous logical derivation and a preliminary determination of the operation flow, there are still many problems to be continued to be studied and solved, such as the refinement of the internal parameters of RM, the expansion of the structure to the third layer. The fourth layer or even the outer layer, etc. After perfecting these theories and methods, the method presented in this paper can be applied to a wide range of material fields.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O434.1;TN304

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