Silica thin films were first deposited on a poly(ethylene terephthalate! sheet and silicon wafer substrates by the reduction of an aqueous ammonium hexafluorosilicate solution by dimethylamine borane at 323 K. The time course of film growth was measured by X-ray fluorescent (XRF) spectrometry and an enhancement of deposition rate by coating the substrates with catalyst was observed. Characterization of films by X-ray photoelectron spectroscopy (XPS) and infrared (IR) absorption spectroscopy proved that the film consisted mainly of SiO2 and a surface hydroxyl group. Reactions for film deposition focused on pH shift by reduction of the solution were proposed. (C) 2004 The Electrochemical Society.