Structural and electronic characteristics of ZnO thin films dc sputtered on sapphire (0001) substrates

Abstract

Using reactive de magnetron sputtering, we observed the epitaxial growth of ZnO films on Al2O3 (0001) substrates at several temperatures ranging from 300 to 600 degrees C. The structural properties and the quality of the ZnO thin films were characterized by using X-ray diffraction (XRD). XRD measurements showed that the ZnO films were highly c-axis-oriented with in-plane epitaxy and that the linewidth of the (0002) peak was sensitive to a variation in the substrate temperature. Based on the full-width at half-maximum of (0002) peak, the best crystal quality of the ZnO films was obtained at a growth temperature of 500 degrees C and the lattice strain was linearly relaxed as the growth temperature increased. Near-edge X-ray absorption fine structure (NEXAFS) spectra confirmed the XRD result for the growth orientation by showing that the c-axis of the ZnO film was normal to the surface of the film, at least in the neighborhood of the absorbing atom. The Hall-effect measurement revealed that the mobility of the deposited films was 4.14 cm(2)V(-1)s(-1).