Structural and electrical properties of Zn(Al)O layers for transparent metal oxide applications

Abstract

The microstructure and electrical properties of low temperature (250 degrees C) RF sputtered At doped ZnO layers are investigated. By varying the At composition from 0 to 15 at%, it is shown that the morphology of the layers is improved whereas the crystalline structure changes from highly oriented monocrystalline domains to textured and misoriented nanocrystallites. It is also noticed that the best metallic properties are attained for a quite low At concentration in the AZO (3 at%), when the At content is further increased, the mobility, carrier density and resistivity saturate. The annealing in air at higher temperatures does not seem to improve the conduction properties, instead at 800 degrees C, the resistivity drops by more than one order of magnitude and the carrier density by almost five orders of magnitude. At this high temperature, the strong increase of the mobility is tentatively attributed to the better crystalline quality of the annealed layers. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.