Growth and photoluminescence of ZnO thin films on Si(111) by PLD in oxygen adequate ambient

Polycrystalline ZnO thin films were synthesized on Si(1 1 1) substrates by pulsed laser deposition (PLD) under oxygen sufficient condition at temperatures ranging from 550 to 700 degrees C. The results of in situ reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) show that the (0 0 2) orientation of ZnO thin films is deteriorated, but the full-width at half-maximum (FWHM) of (0 0 2) peak decreases as the substrate temperature (T-s) increases. In photoluminescence (PL) spectra at room temperature (RT), all the ZnO thin films show small ultraviolet (UV) peak FWHMs in the range of 83-95 meV. The thin film prepared at 650 degrees C exhibits the narrowest UV peak FWHM of 83 meV and the biggest intensity ratio (122) of UV emission (UVE) to deep-level emission (DLE). When the T-s increases to 700 degrees C, a low-energy peak in the UV region at around 381 nm (3.25 eV) appears, which maybe result from a donor-acceptor-pair (DAP) transition and be a signal of excess incorporation of oxygen in the thin film. (c) 2007 Elsevier Ltd. All rights reserved.