Electrochromic molybdenum oxide (MoO3) thin films were prepared by electron beam evaporation technique using the dry MoO3 pellets. The films were deposited on glass and fluorine doped tin oxide (SnO2:F or FTO) coated glass substrates at different substrate temperatures like room temperature (RT, 30 degrees C), 100 degrees C and 200 degrees C. The influence of substrate temperature on the structural, surface morphological and optical properties of the films has been studied. The X-ray diffraction analysis showed that the films are having orthorhombic phase MoO3 (alpha-MoO3) with (110) preferred orientation. The laser Raman scattering spectrum shows the polycrystalline nature of MoO3 films deposited at 200 degrees C. The Raman-active band at 993 cm(-1) is corresponding to Mo-O stretching mode that is associated with the unique character of the layered structure of orthorhombic MoO3. Needle-like morphology was observed from the SEM analysis. The energy band gap of MoO3 films was evaluated which lies between 2.8 and 2.3 eV depending on the substrate temperature and substrates. The decrease in band gap value with increasing substrate temperature is owing to the oxygen-ion vacancies. The absorption edge shift shows the coloration effect on the films. (c) 2005 Elsevier B.V. All rights reserved.