Structural and optical properties of ZnO:Mg thin films grown under different oxygen partial pressures

Pure and Mg-doped zinc oxide (ZnO:Mg) films were deposited using RF reactive magnetron sputtering at different oxygen partial pressures. The microstructures and optical properties in doped ZnO films were systematically investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and fluorescence spectrophotometer. The results indicated that ZnO grain orientation behavior was significantly affected by Mg-doping. And the ZnO:Mg film prepared at 15:10 had the best crystal quality among all ZnO:Mg films. The photoluminescence (PL) measurements at room temperature revealed a violet, two blue and a green emission. The origin of these emissions was discussed. It was also demonstrated that the optical band edge shifted to a shorter wavelength first as Mg was incorporated, and then to a longer wavelength with the increasing of oxygen partial pressures.