Effect of Annealing Duration and Substrates on Structure and Property of Vanadium Dioxide Films

Using the oxidation method from vanadium metal thin films by magnetron sputtering, under the fixed annealing parameters of temperature (400 °C) and oxygen pressure (103 Pa), we fabricated a series of vanadium dioxide thin films through the change of annealing durations or substrates (quartz glass or AZO-covered glass). Characterization of the thermochromic properties together with the X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) indicates that appropriate annealing duration is a key factor to obtain pure VO2 films and AZO-covered glass is more suitable to obtain the VO2 films with high visible transmittance, good crystallinity and larger near-infrared switching efficiencies (maximum 34% at 2000 nm) compared with the substrate of quartz glass. However, VO2 films on quartz glass exhibit narrower loop (7 °C) with smart reversible response to temperature. Depth profile XPS spectra further indicate that for the films fabricated on quartz glass from thicker V metal films, the existence of low valence vanadium oxides is inevitable and leads to a lower transmittance in the region of visible light.