Transparent conducting ZnO thin films doped with Al have been prepared by sol-gel method, which were characterized by X-ray diffraction, atomic force microscopy and ultra-violet spectrometer. The films showed a hexagonal wurtzite structure and high preferential c-axis orientation. The optical transmittance spectra of the films showed the transmittance higher than 85% within the visible wavelength region. A minimum resistivity of 6.2 x 10(-4) Omega CM was obtained for the film doped with 1.5 mol.% Al, preheated at 300 degrees C for 15 min and post-heated at 530 degrees C for 1 h. (c) 2005 Elsevier Ltd. All rights reserved.