Electrosynthesis of MO(IV) oxide thin films on F-doped SnO2 conducting glass (10-20/Omega/rectangle) substrates were carried from aqueous alkaline solution of ammonium molybdate at room temperature. The physical characterization of as-deposited films carried by thermogravimetric/differential thermogravimetric analysis (TGA/DTA), infrared spectroscopy and X-ray diffraction (XRD) showed the formation of hydrous and amorphous MoO2. Scanning electron microscopy (SEM) revealed a smooth but cracked surface with multi-layered growth. Annealing of these films in dry argon at 450 degrees C for 1 h resulted into polycrystalline MoO2 with crystallites aligned perpendicular to the substrate. Optical absorption study indicated a direct band gap of 2.83 eV The band gap variation consistent with Moss rule and band gap narrowing upon crystallization was observed. Structure tailoring of as-deposited thin films by thermal oxidation in ambient air to obtain electrochromic Mo(VI) oxide thin films was exploited for the first time by this novel route. The results of this study will be reported elsewhere. (c) 2005 Elsevier B.V. All rights reserved.