Effects of post-annealing treatment on the structural and optical properties of cubic Mg chi Zn1-chi O thin films grown on sapphire

Single cubic-phase MgxZn1-xO(x 0.5) alloy films were synthesized on c-plane sapphire substrates by low temperature physical deposition. The effects of the post-annealing treatment on the structural properties of the films were investigated by the measurements of XRD and transmission spectra. Hexagonal-phase (wurtzite) MgZnO was observed segregating from the cubic-phase Mg0.53Zn0.47O film after annealing at 900℃, while no secondary phase was seen in the samples with Mg fraction exceeding 0.55. Electrical measurement indicates that cubic-phase Mg0.55Zn0.45O films can be used in metal-insulator-silicon (MIS) structures as insulators with low leakage current densities. It could be concluded that the cubic-phase MgxZn1-xO films with x exceeding 0.55 are stable enough to be applied in fabricating high quality optoelectronic devices.