Intelligent window coatings: Atmospheric pressure chemical vapour deposition of vanadium oxides

Thin films of the vanadium oxides, V₂O₅, VO₂, VO_x (x = 2.00-2.50) and V₆O₁₃ were prepared on glass substrates by atmospheric pressure chemical vapour deposition (APCVD) of vanadium tetrachloride and water at 400-550°C. The specific phase deposited was found to be dependent on the substrate temperature and the reagent concentrations. The films were characterised by Raman microscopy, x-ray diffraction (XRD), Rutherford backscattering (RBS), scanning electron microscopy (SEM), energy dispersive analysis by x-rays (EDX), reflectance/transmittance and UV absorption spectroscopy. The VO₂ films show by Raman microscopy and reflectance/transmittance spectroscopy, reversible switching behaviour at 68°C associated with a phase change from monoclinic (MoO₂ structure) to tetragonal (TiO₂, rutile structure).