Molybdenum oxide films (MoO(3)) were deposited on glass and crystalline silicon substrates by sputtering of molybdenum target under various oxygen partial pressures in the range 8 x 10(-5)-8 x 10(-4) mbar and at a fixed substrate temperature of 473 K employing dc magnetron sputtering technique. The influence of oxygen partial pressure on the composition stoichiometry, chemical binding configuration, crystallographic structure and electrical and optical properties was systematically Studied. X-ray photoelectron spectra of the films formed at 8 x 10(-5) mbar showed the presence of Mo(6+) and Mo(5+) oxidation states of MoO(3) and MoO(3-x). The films deposited at oxygen partial pressure of 2 x 10(-4) mbar showed Mo(6+) oxidation state indicating the films were nearly stoichiometric. It was also confirmed by the Fourier transform infrared spectroscopic studies. X-ray diffraction studies revealed that the films formed at oxygen partial pressure of 2 x 10(-4) mbar showed the presence of (0 k 0) reflections indicated the layered structure of alpha-phase MoO(3). The electrical conductivity of the films decreased from 3.6 x 10(-5) to 1.6 x 10(-6) Omega(-1) cm(-1), the optical band gap of the films increased from 2.93 to 3.26 eV and the refractive index increased from 2.02 to 2.13 with the increase of oxygen partial pressure frorn 8 x 10(-5) to 8 x 10(-4) mbar, respectively. (C) 2009 Elsevier B.V. All rights reserved.