Structural, electrical and photoluminescence properties of ZnO:Al network films grown on nanochannel Al2O3 substrates by direct current magnetron sputtering with an oblique target

Abstract

ZnO:Al network films were grown on nanochannel Al2O3 substrates at 300K by direct current magnetron sputtering with an oblique target. The film thicknesses are 60nm, 160nm and 190nm. The holes of the network films diminish with increasing film thickness. For the 60-nm thick film, the network is formed by connecting grains. For the 160-nm and 190-nm thick films, however, the network is formed by connecting granules. The granules consist of many small grains. All the network films have a wurtzite structure. The 60-nm and 160-nm thick network films mainly have a [101] orientation in the film growth direction while the 190-nm thick network film grows with a random crystallographic orientation. A temperature dependence of the resistance within 160–300K reveals that the network films exhibit a semiconducting behavior and their carrier transport mechanism is thermally activated band conduction. Room temperature photoluminescence spectra for wavelengths between 300nm and 700nm reveal a violet emission centered at 405nm for the 60-nm thick network film and a blue emission centered at 470nm for both the 160-nm and the 190-nm thick network films. Annealing decreases the resistivity of the network film.