Influence of SiO2 buffer layer on the crystalline quality and photoluminescence of ZnO thin films

In this work, a SiO2 buffer layer was first grown on Si substrate by thermal oxidation, and then ZnO thin films were deposited on SiO2 buffer layer and Si substrate by electron beam evaporation and sol-gel method. The influence of SiO2 buffer layer on the crystalline quality and photoluminescence of the films was investigated. The analyses of X-ray diffraction (XRD) showed that all the ZnO thin films had a hexagonal wurtzite structure and were preferentially oriented along the c-axis perpendicular to the substrate surface. The SiO2 buffer layer improved the crystalline quality and decreased the stress in ZnO thin films. The surface morphology analyses of the samples indicated that ZnO thin films deposited on SiO2 buffer layers had densely packed grains which obviously increased compared with those grown on bare Si substrate. The photoluminescence spectra of the samples showed that the ZnO thin films deposited on SiO2 buffer layers had stronger ultraviolet emission performance. The results suggest that SiO2 buffer layer can improve the crystalline quality and ultraviolet emission of ZnO thin films.