Annealing induced optical properties of YSZ thin films prepared by EB-PVD

In this study, YSZ thin films with different Y2O3 content have been prepared by electron beam evaporation on different types of substrates. The film properties such as surface roughness, microstructure, refractive index and transmission spectra were characterized by using Scanning Probe Microscopy (SPM), X-ray diffraction, SEM, ellipsometer and spectrophotometer respectively. The results indicate that the film properties and microstructure correlate with the annealing process dramatically. It is found the film structure undergoes from amorphous to tetragonal phase then ultimately to tetragonal and monoclinic phase with the temperature increasing from 100 to 1100°C, while the surface roughness increases from 1.3 to 24.6nm, and the refractive index varies from 1.86 to 2.02. XRD analysis shows the grain size increased with the annealing temperature, the reduction of defect and surface compact incurred by the high temperature process results in the increase of refractive index. Further investigations show that the optical properties of YSZ films have little effect with the content of Y2O3 and the variation of refractive index is caused by the compactness due to the crystallization of the films under high temperature.