The influence of temperature on the dielectric properties of sol-gel routed spin-coated molybdenum trioxide (MoO 3 Þ thin film has been investigated. Prepared films were annealed at temperatures 250 C, 350 C and 400 C. The phase transformation from amorphous to -orthorhombic phase with preferential orientation (0 2 2) has been found by XRD for the film annealed above 250 C. The vibration modes of -orthorhombic MoO 3 have been examined by Raman spectrum. The predominant Raman's band of -orthorhombic MoO 3 thin film has been found at the frequency range 1000-600 cm À1 . Using the UV-Vis spectrum, the band gap of the film is found to be 3.3-3.8 eV. The surface morphology of the MoO 3 films has been examined by scanning electron microscope. The AC conductivity measurement of the MoO 3 film has been carried out in the frequency range 10-10 6 Hz. The frequency dependence of the impedance has been plotted in the complex plane. The variation of the capacitance and dielectric constant of MoO 3 film with respect to temperature and frequency has been analyzed. Tunability of capacitance and figure of merit of the film are also determined.

The in°uence of annealing temperature on structural and optical properties of sol-gel routed spincoated molybdenum tri oxide (MoO 3 ) thin¯lms are studied. The higher annealing temperatures improve the crystalline nature of the¯lm. The X-ray di®raction (XRD) study reveals the formation of -orthorhombic phase at higher annealing temperature and amorphous nature at lower annealing temperature. The optical bandgap of molybdenum tri oxide (MoO 3 )¯lm is found to be 3.3-3.8 eV, and the refractive index of the¯lm is found to be 2.2-2.9. The dispersion curve of the refractive index shows that an abnormal dispersion in the absorption region and normal dispersion in the transparent region are observed. The optical polarizability, optical conductivity, dielectric constant, volume and surface energy loss parameters are evaluated.