Effects of oxygen partial pressure and substrate temperature on the structure and optical properties of MgxZn1−xO thin films prepared by magnetron sputtering

Deposited with different oxygen partial pressures and substrate temperatures, MgxZn1−xO thin films were prepared using a Mg0.6Zn0.4O ceramic target by magnetron sputtering. The structural and optical properties of the prepared thin films were investigated. The X-ray diffraction spectra reveal that all the films on quartz substrate are grown along (2 0 0) orientation with cubic structure. The lattice constant decreases and the crystallite size increases with the increase of substrate temperature. Both energy dispersive X-ray spectroscopy and calculated results suggest the ratio of Mg/Zn increases with increasing substrate temperature. The thin film deposited with Ts = 500 °C has a minimal rms roughness of 7.37 nm. The transmittance of all the films is higher than 85% in the visual region. The optical band gap is not sensitive to the oxygen partial pressure, while it increases from 5.63 eV for Ts = 100 °C to 5.95 eV for Ts = 700 °C. In addition, the refractive indices calculated from transmission spectra are sensitive to the substrate temperature. The photoluminescence spectra of MgxZn1−xO thin films excited by 330 nm ultraviolet light indicate that the peak intensity of the spectra is influenced by the oxygen partial pressure and substrate temperature.

Research highlights► The lattice constant and crystalline size of MgZnO thin films as a function of oxygen partial pressure and substrate temperature are investigated. ► Both the calculated and measured results show the ratio of Mg/Zn is influenced by the substrate temperature. ► The intensity of photoluminescence spectra is influenced by the oxygen partial and substrate temperature and associated with defect density and film quality.