Optical performance of nanocrystalline transparent ceria films

Abstract

Ceria is a transparent oxide suitable for various optical and optoelectronic devices. In this work, we tailor independently the refractive index n and fundamental gap Eg of nanocrystalline Ceria films by varying the substrate temperature or using Ar+ ion beams during growth with electron beam evaporation. Spectroscopic ellipsometry and x-ray reflectivity are employed to study n and Eg and to identify the physical parameters that affect them. We correlate n (varies from 1.65 to 2.15 in the studied films) with the film density through a universal, square law. The film composition strongly affects Eg, which varies from 2.8 to ∼2.0 eV. The optical absorption below 3 eV and the Eg shift are attributed to O-defect states and not to modifications in interband transitions. © 2002 American Institute of Physics.