Thermal annealing effect on the crystallization and optical dispersion of sprayed V2O5 thin films

Polycrystalline vanadium pentoxide (V2O5) thin films have been deposited by spray pyrolysis technique on preheated glass substrate. The influence of thermal annealing on the crystallization of V2O5 has been investigated. X-ray diffraction analysis (XRD) revealed that the films deposited at Tsub=350 °C were orthorhombic structures with a preferential orientation along 〈0 0 1〉 direction. Moreover, the degree of crystallinity was improved by thermal annealing. Optical properties of these samples were studied by spectrophotometer in the wavelength range 300–2500 nm. Some of the important optical absorptions such as optical dispersion energies Eo and Ed, dielectric constant ε, ratio between number of charge carriers and effective mass N/m*, wavelength of single oscillator λ0, plasma frequency ωp, single resonant frequency ω0 and the average of oscillator strength So, have been evaluated. In the annealing process, the dielectric properties have weak dependencies of film thickness and annealing time. Furthermore, a value of carrier concentration was obtained of 3.02×1025 m−3 for the as-deposited film and slight changes with annealing time.