Annealing temperatures effect on the electrical and structural properties of nanocrystalline vanadium dioxide films prepared by Sol–Gel technique

Vanadium oxide (VO${}_2$) films glass substrate deposition was achieved at room temperature by the sol–gel method. The fabricated VO${}_2$ films were annealed for 1 h at 200, 250, and 300 °C in air. The annealing temperature's effects on the electrical and structural properties of VO${}_2$ films were investigated by DC conductivity, dielectric, AC conductivity, and X-ray diffraction (XRD). XRD results of the annealed films reveal the presence of polycrystalline VO${}_2$ with a monoclinic structure. Using the Scherrer equation, an average grain size of VO${}_2$ films was estimated to be 2.1–10.8 nm. The density of annealed films was found to be 4.53–4.75 g/cm${}^3$. The DC-electrical conductivity reveals the semiconductor behavior of all samples. The activation energy of the prepared films was deduced as 0.22–0.38 eV. The DC conductivity for the VO${}_2$ films decreases at an annealed temperature higher than 200 °C, which may due to the increase in grain boundary scattering due to the increase in grain size. The dielectric measurements show that the dielectric loss and dielectric constant decline with the increasing frequency however of these parameters with the annealing temperature. Moreover, the increasing of the AC conductivity with the temperature and frequency is observed. These results suggest that the mobility of charge carriers was increased.