电子背散射衍射的高精度相鉴定研究

Electron Backscatter Diffraction, as a powerful tool for the analysis of crystalline material on the nanometer scale, is still very difficult in determining the unknown phase of the sample. If the maximum amount of information can be extracted from the experimental electron backscatter diffraction (EBSD) patterns, the EBSD technique will be arrive in a new limits for identifying and determining phase. The object of this project to solve the key problem about how to simulate the relative intensities of EBSD patterns precisely. By considering the influence of the energy spectrum of the backscattered electrons, the dynamical effection of anisotropic backscattering and the loss of electrons from the initial population due to inelastic effects, the full scale EBSD patterns will be simulated and the precise lattice parameter of the sample will be obtained using an accurate Multislice method for low-energy transmission electron microscopy. A new software package of EBSD analysis will be established with the function of phase identification and determination precise.

电子背散射衍射(EBSD)技术作为一种进行纳米尺度材料显微组织结构分析的强有力工具，在用于未知相的鉴定方面一直非常困难。如果能最大限度地提取出衍射花样中的信息，那么EBSD技术不仅在进行已知相的识别，而且在进行未知相的鉴定方面都将达到一个全新的高度。本申请项目以解决怎样精确模拟EBSD衍射花样的相对强度这一关键问题为目标，通过采用适应于低能电子动力衍射模拟的多片层方法，充分考虑各种客观因素（如：背散射电子能量展宽、各向异性背散射和弹性散射过程中样品的吸收等）的影响，精确模拟全尺度的EBSD图，获得进行精确相鉴定所需的晶体点阵常数，开发出具有高精度相鉴定功能（对已知相进行识别，对未知相进行鉴定）的EBSD分析软件。

通过采用电子动力衍射理论对背散射电子衍射花样进行模拟可以从其中最大限度地获取晶体学信息。本项目中，我们首先对现有的各种电子动力衍射模拟算法进行了对比和修正，并对其中某些算法的应用领域进行了拓展。然后，用两种多片层方法（包括实空间法和修正的实空间法）成功地模拟了背散射电子衍射花样。通过改变加速电压、得拜瓦乐因子和光阑半径，我们对分别采用两种方法模拟的计算结果进行了详细地分析和比较。研究结果表明在计算时间可接受的情况下，用改进的实空间法模拟的EBSD花样比用实空间法模拟的花样更准确。最后，通过考虑入射电子束能量展宽，入射束倾斜角度，样品厚度等因素对模拟的EBSD花样进行了精修。