Effects of Homo-buffer Layer on Properties of ZnO Films Grown on Si(1 1 1) by Pulsed Laser Deposition

ZnO films have been synthesized on Si(111) substrates at 650 degC by pulsed laser deposition (PLD). ZnO homo-buffer layers deposited at a low temperature of 500 degC under oxygen pressures between 15 and 60 Pa were employed for the growth. Influence of the buffer layer on the properties of ZnO films was investigated. The results of X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) indicate that epitaxial ZnO films can be achieved when the buffer layers are deposited at 15, 30, and 45 Pa. In photoluminescence (PL) spectra at room temperature, the ZnO film shows the strongest ultraviolet (UV) emission and the narrowest UV peak full width at half maximum (FWHM) of 97 meV, when the buffer layer is prepared at 45 Pa. The enhancement of UV emission from the film is assigned to the reduction of non-radiative recombination centers, and the detailed reasons are discussed