Application of optical and luminescent techniques to the characterization of oxide thin films

Abstract

The interaction between light and electrons in oxide compounds forms the basis for many interesting and practical effects, which are related to microstructure, energy band, traps, carrier transport and others. Thin films of oxides like WO3, Ga2O3, Y2O3 and SrTiO3 were investigated using various improved optical and luminescent techniques. The home-made systems for optical and luminescent measurements were described in detail. The facilities of photo-Hall and photoconductivity transients have been proven to be powerful tools in the studies, which allow us to perform photoinduced process and relaxation measurements over a wide time range from 10−8 to 104 s. Furthermore, we extended the measurement capabilities of the commercial luminoscope by using an interferometer system with optical fiber and illuminance meter instead of an optical microscope. The cathodoluminescent measurements can be performed at a relative high pressure (20–60 mTorr) compared to ultra-high-vacuum condition of most commercial products. Luminescent characterization was employed as a probe to study doping ions, oxygen vacancies, trap and/or exciton levels in oxide thin films. Our results suggest that various traps and/or excitons in thin films of WO3, Ga2O3 and SrTiO3 involve in the process of photoconductivity relaxation and emission.