Vanadium Oxide Thin Films via the Epoxide Route: Tailoring Oxide Properties through Substrate and Thermal Treatment

Abstract

This work presents a novel synthetic method to produce vanadium oxides thin films with different crystallographic phases and temperature sensitivities, by using a single precursor solution and different processing conditions. The Epoxide Route was employed to homogeneously produce a V(III) hydroxide sol, as demonstrated using X-ray absorption and scattering. Subsequently, films were prepared by spin coating sols aged for different times, showing that uniformity is achieved when the sols are deposited near the gelation point. The effect of the substrate and the annealing conditions over the identity of the obtained oxide was investigated by X-ray diffraction. The findings indicate that pure V₂O₅ can be synthesized through annealing in air, while pure VO₂ is formed under inert conditions, when both bare and silicon-nitride-passivated silicon substrates were used. On the other hand, oxides formation was inhibited on glass substrates, probably due to ion migration. Finally, the electrical properties as a function of temperature were assessed. The results show a significant change in resistivity for VO₂ thin films attributed to a well-known structural phase transition, whereas V₂O₅ thin films exhibited a thermally activated electrical behavior. The proposed methodology allows easily producing vanadium-based thin films suitable for applications in devices that require temperature sensitivity.