Effect of Firing Temperature on the Structural, Optical, and Electrical Properties of VO<sub>2</sub> Thin Films Deposited by Chemical Solution Deposition

Characteristics of VO2 films prepared on alkali-free glass substrates by chemical solution deposition (CSD) using vanadyl oxalate n-hydrate as the raw material are investigated. Diffraction peaks corresponding to VO2 are observed in the samples obtained at firing temperatures of 350 to 550°C. However, diffraction peaks of the samples obtained at 500 and 550°C show a mixture of VO2 and V6O13 phases. Regarding the surface and cross-section morphology of the films, the crystal grain size and porosity of the films steadily increase with firing temperature. The samples show an abrupt change in resistivity around 70°C. The change in resistivity caused by the metal-insulator transition are about three orders of magnitude. The sample transmittance in the near-infrared region decreases sharply with the phase transition. The maximum reduction in transmittance at 2000 nm is 55.4%.