Effects of annealing on the structural and photoluminescence properties of Zn0.98Cr0.02O thin films prepared by magnetron sputtering

Cr-doped ZnO thin films have been prepared on silicon substrates by magnetron sputtering method. The effects of annealing on the compositions, crystallographic structures, and optical properties of the thin films are systematically investigated by energy dispersive spectroscopy, X-ray diffraction, and photoluminescence, respectively. The results show that the intensity of ZnO(002) peak firstly increases and then decreases with increasing the annealing temperature, whereas the full width at half maximum and the stress firstly decrease and then increase with the annealing temperature increasing. The higher crystallization quality and minimum stress was found for the samples annealed at 600 degrees C in oxygen ambient. It is also found from the photoluminescence spectra that the ultraviolet emission peak and green emission band are located at 380 nm and 500 nm, respectively. Further investigations indicate that the nature of the green emission is connected with the concentration of oxygen vacancies. In addition, the excellent luminescence performance of Cr-doped ZnO thin films can be obtained by high temperature annealing at 600 degrees C in oxygen ambient, which can make green emission weakened gradually and even disappeared. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim