The structural, optical and electrical properties of polycrystalline ZnO thin films deposited by metal organic chemical vapor deposition are studied. The surface roughness of the as-deposited ZnO thin films reduces with the increase of growth temperature from 200 to 400 degrees C, and increases with further increase of the growth temperature from 400 and 500 degrees C. All the films possess a transmittance near 100% in the visible region except the samples grown at temperatures of 450 and 500 degrees C. The resistivity of ZnO thin films decreases with the increase of growth temperature. The optical band gap energy of the as-grown ZnO blue-shifted from 3.295 to 3.447 eV as the growth temperature decreased from 500 to 200 degrees C, which is due to the increase of localized states in the conduction band, associated with the amorphitization of the film. (c) 2005 Elsevier B.V. All rights reserved.