Effect of a ZnO buffer layer on the properties of Ga-doped ZnO thin films grown on Al2O3 (0001) substrates at a low growth temperature of 250 degrees C

Abstract

4 wt% Ga-doped ZnO (GZO) thin films have been prepared on the buffered and non-buffered Al2O3 (0 0 0 1) substrates by RF magnetron sputtering technique at a low growth temperature (250 degrees C). The effect of a ZnO buffer layer on the crystallinity, optical, and electrical properties of the GZO thin films is investigated. X-ray diffraction and transmission electron microscopy studies showed that the GZO thin film on a buffered substrate was epitaxially grown at a low growth temperature of 250 degrees C with an orientation relationship of (0001)[1 (1) over bar 20](GZO)parallel to(0001)[11 (2) over bar0](Al2O3). However, the GZO thin film on a non-buffered substrate was grown as a polycrystalline hexagonal wurtzite phase with c-axis preferred, out-of-plane orientation, and random in-plane orientation. The optical transmittance in the visible region and the electrical resistivity of the GZO thin film was improved by introducing a ZnO buffer layer from 70% to 80% and from 4.69 x 10(-3) to 1.01 x 10(-3) Omega cm, respectively. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.