Optical properties and structure of indium oxide films obtained under various conditions of magnetron sputtering

In this paper we summarize the studies of the structural and optical properties of In$_2$O$_3$ films on Al$_2$O$_3$ (012) substrates obtained by dc magnetron sputtering. According to X-ray diffraction, deposition time effects on the position and half-width of the (222) peak of cubic In$_2$O$_3$. Ellipsometric measurements and analysis of optical transmission spectra show that films obtained at temperatures of 300$^\circ$C or more have uniform optical properties, except the surface layer. The refractive index of films obtained at room temperature increases along the direction from the substrate to the surface. Annealing eliminates this inhomogeneity, reduces the observed band gap due to a decrease in the concentration of lattice defects, but do not effects on the true band gap.