Optical and structural inhomogeneity in reactive evaporated and IAD CeO2 films analyzed by x-ray diffraction and reverse optical engineering

Evaporated CeO2 films are known to show a pronounced optical inhomogeneity in dependence on the chosen deposition parameters, especially in dependence on the substrate temperature during deposition. Samples were manufactured by reactive electron beam evaporation and by ion assisted deposition onto substrates held at different temperatures. Optical analysis of spectral transmittance and reflectance data supplemented by x-ray diffraction and infrared measurements were carried out on the basis of an inhomogeneous refractive index layer model. Using the Wemple - DiDomenico single oscillator dispersion formula together with an effective medium approach for porous materials the inner part of the films at the substrate interface was found to show "void-like" behaviour, while most of the film show "crystallite-like" behaviour in accordance with the columnar growth observed with evaporated CeO2 - films. By IAD the optical as well as the crystalline properties of the deposited films were modified.