Coating of vanadium dioxide thermochromic thin film on glass via sol-gel method

Vanadium oxide nano-coating which has a monoclinic to tetragonal (rutile) transition at about 68 °C was successfully coated on a soda lime glass via sol-gel method. Grazing incidence X-ray diffraction results showed that two phases were coexisted in the coating named VO2 and V6O13 which due to the overlap of their patterns, diffuse reflectance spectroscopy was used to determine the main phase. According to diffuse reflectance spectroscopy results, band gap energy of the coating was about 1.65 eV and which was related to semiconductor phase (VO2), because V6O13 show a metallic behavior at room temperature. 4-point resistivity showed that the coating surface resistance was decreased from 1 MΩ to about 200 Ω. Microstructural analysis showed that the coating was uniform and the crystallite size was about 40-70 nm. According to atomic force microscopy results, the mean roughness of the surface and the maximum roughness were about 18 nm and 120 nm, respectively.