Undoped vacuum annealed In2O3 thin films as a transparent conducting oxide

We have investigated the structural, optical, and electrical properties of both as-grown and vacuum annealed ${\text{In}}_2{\text{O}}_3$ thin films. In contrast to the insulating as-prepared samples, vacuum annealed ${\text{In}}_2{\text{O}}_3$ films exhibit a metallic electrical conductivity with increased carrier concentration and mobility. We attribute the excess carriers to an oxygen deficiency introduced during vacuum annealing. Remarkably, these carrier densities seem to be stable under ambient conditions for at least two years. Optical spectroscopy measurements show a large optical transparency, greater than 80%, for both the as-prepared and vacuum annealed ${\text{In}}_2{\text{O}}_3$ films.