Determination of the dielectric tensor function of crystals with arbitrary structure and orientation based on reflectance measurements

确定单晶振子参数(色散分析)的目的有两个。首先，这些参数的知识可以用来分析晶体的结构性质关系，其次，由于这些参数描述了介电张量在特定光谱范围内的函数，因此可以计算单晶和多晶织构或随机取向材料的反射、透射率和散射等光学性质。最近，基于反射率测量评估的色散分析被扩展到三斜晶体，因此可以应用于所有晶体，无论其晶体结构如何。然而，除了三斜(和微不足道的立方)单晶外，所有其他物种都需要在色散分析之前进行定向。这种取向通常是借助X射线衍射法进行的。在第二步中，需要沿着和垂直于某些晶轴和晶面切割取向的晶体。该项目的目标是开发一种不需要取向步骤的程序，最终，晶体结构和取向的确定也是通过随后的色散分析的反射光谱来确定的。在第一个项目中，相色散分析将进一步发展到如果晶体的晶体结构已知，则可以在没有预先取向的情况下进行该分析的点。第二阶段的目标包括采用和增强三斜晶体的振子模型，从而以这样一种方式进行色散分析，即既不了解晶体结构也不了解取向，这是成功进行色散分析所必需的先验知识。

The goal of the determination of oscillator parameters of a single crystal (dispersion analysis) is twofold. First the knowledge of these parameters can be used to analyze the structure properties relationships of the crystal and, second, as the parameters describe the function of the dielectric tensor in a certain spectral range, to calculate optical properties like reflectance, transmittance and scattering for single crystals and polycrystalline textured or randomly oriented materials.Recently, dispersion analysis based on the evaluation of reflectance measurements was extended to triclinic crystals and can therefore be applied to all crystals regardless their crystal structure. However, apart from the triclinic (and, trivially, cubic) single crystals, all other species need to be oriented prior to dispersion analysis. This orientation is usually carried out with help of X-ray diffraction methods. In a second step the oriented crystals need to be cut along and perpendicular to certain crystal axes and planes.The goal of the project is to develop a procedure for which an orientation step is not necessary and, eventually, also the determination of crystal structure and orientation is determined by reflectance spectroscopy with a subsequent dispersion analysis.In the first project phase dispersion analysis will be further developed to the point where it is possible to carry it out without prior orientation of a crystal if its crystal structure is known. The goal of the second phase consist of adapting and enhancing the oscillator model for triclinic crystals and thereby dispersion analysis in a way that knowledge of neither crystal structure nor orientation is a priori necessary to successfully conduct a dispersion analysis.