Electrical and optical properties of ZnO thin films prepared by magnetron rf sputtering - influence of Al, Er and H

The influence of Al, Er and H in ZnO thin films (ZnO:Al, ZnO:Er and ZnO:H) deposited by magnetron sputtering at different substrate temperatures, T-s, on their optical, structural and electrical properties was investigated. X-ray diffraction (XRD) analyses show an improvement of the crystalline structure with increasing T-s. The optical band gap, E-opt, of the films, from transmission and reflection spectra, ranged from 3.27 to 3.41 eV. The Urbach band tail width was also calculated. Incorporation of Al and Er resulted in a reduced and an increased resistivity, rho, respectively, and an increase in the Urbach tail width in both cases. However, sputtering in an Al + H-2 gas mixture led to an increase in p and an improvement in the structural order of the films. A discussion of the influence of T-s and of Al, Er and H on the properties is presented. (c) 2007 Elsevier Ltd. All rights reserved.