Sub-stoichiometric molybdenum trioxide (MoO3−x) thin films were grown by thermal evaporation
techniques on glass, single crystal silicon Si and Fluorine doped Tin Oxide (FTO) glass substrates with
different thicknesses. It was found that, Oxygen vacancies play an important role on properties of
MoO3−x films. The structural properties of these films were analyzed by means of x-ray diffraction,
energy dispersive analysis of x-ray, scanning electron microscopy. The film surface uniformity and
smoothness with thickness was tested using the surface roughness measurement forMoO3−x films
grown on glass and FTO. The optical properties of all presented films were investigated usingUV–vis–
near-infrared (NIR) spectrophotometer Optical transmittance and reflection ofMoO3−x film were
measured in the wavelength range from 200 to 2500 nm.MoO3−x film with 500nmthick was tested
optically for gas sensor applications. The effect of chlorine exposure on the optical transmittance of
MoO3−x film with 500nmthick deposited on glass was studied. Transmittance degradation as
increasing the period of exposure was observed, indicating to the high sensitivity ofMoO3−x to
chlorine gas. The electrical resistivity and Seebeck coefficient ofMoO3−x film with 500nmthick were
measured. Low resistivity (∼10−3Ω.cm) and high transmittance (∼78%) in the visible spectrum of the
film of 100nmthick deposited on FTO coated glass substrate recommended it to be promising as
transparent conductive electrode for solar cell.