ZnO thin films are deposited in pure Ar and mixed Ar and N-2 gas ambient at various substrate temperatures by rf sputtering ZnO targets. We find that the deposition in pure Ar ambient leads to polycrystalline ZnO thin films. However, the presence of N-2 in the deposition ambient promotes the formation of aligned nanorods at temperatures above 300 degrees C. ZnO films with aligned nanorods deposited at 500 degrees C exhibit significantly enhanced photoelectrochemical response, compared to polycrystalline ZnO thin films grown at the same temperature. Our results suggest that aligned nanostructures may offer potential advantages for improving the efficiency of photoclectrochemical water-splitting for H-2 production. (C) 2007 Elsevier B.V. All rights reserved.