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, Ts, on their optical, structural and electrical properties was investigated. X-ray diffraction (XRD) analyses show an improvement of the crystalline structure with increasing Ts. The optical band gap, Eopt, 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, ρ, respectively, and an increase in the Urbach tail width in both cases. However, sputtering in an Ar+H2 gas mixture led to an increase in ρ and an improvement in the structural order of the films. A discussion of the influence of Ts and of Al, Er and H on the properties is presented.