Violet luminescence emitted from Ag-nanocluster doped ZnO thin films grown on fused quartz substrates by pulsed laser deposition

Silver nanocluster doped ZnO thin films were fabricated on fused quartz substrates at different temperatures by pulsed laser deposition (PLD) using a silver-ZnO mosaic target. X-ray diffraction (XRD) measurements showed that ZnO and doped silver nanoclusters crystallized with preferred c-axis orientation. Scanning electron microscopic (SEM) images of the sample fabricated at 450 degrees C and the X-ray photoelectron spectroscopy (XPS) showed the radius of the silver clusters to be about 3-16 nm. Under 266 nm laser excitation, the photoluminescence (PL) spectra exhibited a peak at 414-420 nm for silver nanocluster doped ZnO thin films deposited at different temperatures. Through the investigation of the energy level of the defects in ZnO thin films, the energy levels of the zinc vacancy (VznEVzn = 3.031eV) and the interstitial zinc atom (Zn-i, E-Zn, = 2.95 eV) were found to be consistent with the peak wavelengths of 414 and 420 run. We suggest that this violet emission originates from an electronic transition between the interstitial-zinc level and the valence band, or between the bottom of the conduction band and the V(Zn)level. (c) 2005 Elsevier B.V. All rights reserved.