Physical investigations on MoO3 sprayed thin film for selective sensitivity applications

Abstract Molybdenum trioxide (MoO 3 ) thin films have been prepared by the spray pyrolysis technique on glass substrates at 460 °C using (NH 4 ) 6 Mo 7 O 24 ·4H 2 O (ACROS pure more than 99.0%) as precursor in the starting solution. X-ray analysis shows that MoO 3 thin film crystallizes in orthorhombic structure with a preferred orientation of the crystallites along (020) and (040) directions. The surface topography of these films was performed by atomic force microscopy and the optical properties were investigated through reflectance and transmittance measurements. The optical band gap energy value is about 3.46 eV and the Urbach energy is of the order of 191 meV. Raman spectroscopy shows the bands׳ positions corresponding to α-MoO 3 phase. PL measurements show two large bands located at 375 nm and 575 nm respectively. Finally, the electric conductivity of MoO 3 thin film was investigated using impedance spectroscopy technique in the frequency range 5 Hz–13 MHz at various temperatures (300–500 °C). The variation of the conductivity in terms of the temperature is characterized by the existence of two ranges with activation energy of 1.00, and 0.42 eV. AC conductivity of MoO 3 thin films is investigated through Jonsher law.