ZnO film was prepared from 0.1 mol dm(-3) zinc nitrate aqueous solution by the potentiostatic technique using a three-electrode system at 313-343 K. The ZnO film was characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In addition, measurements of interface pH and electrochemical quartz crystal microbalance (EQCM) during the electrodeposition were carried out to elucidate the deposition mechanism. It was disclosed that the deposition scheme at the initial stage is quite different depending on bath temperature. The change in deposition mechanism with temperature is closely related to the increased thermodynamic stability of ZnO at high temperature. Based on EQCM analysis, it was suggested that the precursor of ZnO is slowly transformed to ZnO at low temperature, but the formation of ZnO is extremely rapid at high temperature, i.e., ZnO directly deposits at high temperature. Auger analysis indicated that transition from the precursor to ZnO crystal started from the bottom to the surface when the amount of precursor became larger than a critical value depending on temperature. (c) 2006 The Electrochemical Society.