Al-cloped ZnO (AZO) thin films oriented along the (0 0 2) plane have been prepared by the sol-gel process and their electrical and optical properties with post-deposition heating temperature were investigated. The preferred c-axis orientation along the (0 0 2) plane was enhanced with increasing post-deposition heating temperature and the surface of the films showed a uniform and nano-sized microstructure. The electrical resistivity of the films decreased from 73 to 22 Omega cm as the post-deposition heating temperature increased from 500 to 650 degrees C; however, the film postheated at 700 degrees C increased greatly to 580 Omega cm. The optical transmittance of the films postheated below 650 degrees C was over 86%, but it decreased at 700 degrees C. The electrical and optical properties of the AZO filins with post-deposition heating temperature are discussed. (c) 2006 Elsevier B.V. All rights reserved.