Anisotropy micro-ellipsometry for in-situ determination of optical and crystallographic properties of anisotropic solids and layers with Ti/TiO2 as an example

An enhanced micro-ellipsometric method for the investigation of local layer properties on anisotropic solids is introduced. The anisotropy causes the ellipsometric Delta and Psi values to be a function of the sample's rotation around the Euler angles which describe the orientation of the system's permittivity tensor with respect to the surface normal. Quantitative evaluation of these angles by the so-called anisotropy microellipsometry (AME) method allows one to determine the crystallographic properties (orientation of the optical axes) of the substrate and layer as well as optical properties and layer thicknesses. Therefore, AME can be used for the investigation of texture-dependent layer growth. To prove the AME-theory detailed simulations and experiments with the Ti/TiO2 system as an example: are presented. It is possible to distinguish between the different TiO2 layer modifications anatase, brookite, rutile, or amorphous films. Anodically formed oxide layers up to a thickness of 40 nm are amorphous. Layer properties such as density and thickness are quantitatively correlated with the substrate's crystallographic orientation proving the texture dependence of layer growth. Moreover, a UV-laser-induced epitaxial recrystallization of the initial oxides to anatase as well as a further amorphous oxide growth on top of the recrystallized oxides were detected and characterized by AME.