Optical and X-Ray Studies of Indium Oxide Films Deposited by DC Magnetron Sputtering

The results of our studies on the structure and optical properties of In2O3 films deposited by DC magnetron sputtering onto Al2O3 (012) substrates are summarized. The films differ in terms of deposition time and substrate temperature. X-ray diffraction shows that the position and half-width of the peak related to the (222) plane of the cubic modification of In2O3 depends on the deposition time. Ellipsometric and optical transmission measurements show that the refractive index of films deposited on substrates at room temperature increases in the direction from the substrate to the external interface. The refractive index of the films deposited at a substrate temperature of more than 300°C is uniform, except for a rough layer on the surface. Annealing eliminates inhomogeneity of the refractive index and decreases the observed band gap for direct transitions. The latter results from a decrease in lattice defects concentration that causes a change in the Burstein–Moss shift. The true value of the band gap is insensitive to annealing.