High-quality ZnO thin films prepared by low temperature oxidation of metallic Zn

Abstract ZnO thin films were fabricated on Si (1 1 1) substrates by oxidation of metallic Zn films in air. A thin layer of Au was used to enhance the adhesion of the Zn atoms to the Si surface during depositing the Zn films on the substrates at room temperature (RT) by thermal evaporation. X-ray diffraction (XRD) studies indicate that the ZnO film prepared at 500 °C has better crystalline quality than films prepared at other temperatures. In photoluminescence (PL) spectra at room temperature, the film oxidized at 500 °C exhibits the biggest intensity ratio of 162 of ultraviolet (UV) emission to deep-level emission and the narrowest UV peak full width at half maximum (FWHM) of 94.8 meV. These results reveal that high-quality ZnO thin films with good crystallinity and strong UV emission can be achieved at such low temperature. It was also observed that the deep-level emission would become dominant in the PL spectra for the samples annealed at high temperatures above 700 °C, and the possible origin was discussed.