Maximizing Infrared Transmission Contrast upon Phase Transition of Thermally Grown Vanadium Dioxide Thin Films by Rapid Thermal Processing

Pristine vanadium dioxide (VO₂), an insulator-to-metal transition (IMT) material, is grown via furnace oxidation followed by rapid thermal annealing with forming gas (5% H₂/95% N₂) which reduces surface over-oxides such as V₂O₅formed during the oxidation. The evolutional IMT behaviors of the thermochromic film and vanadium oxide states over different reduction times are systematically studied with temperature-dependent infrared spectrometry, electrical resistivity, and X-ray diffraction measurements. After optimally reducing surface over-oxides to VO₂, infrared transmission contrast upon phase transition is enhanced to 46% (at 9 μm wavelength) compared to 23% from full oxidation without any reduction. Moreover, the pristine VO₂thin film obtained from thermal oxidation and optimal reduction processes exhibits sharp phase transition and narrow thermal hysteresis within 2–4 °C in both infrared transmission and electrical resistivity, which are comparable to the best quality VO₂prepared by other sophisticated fabrication techniques. The thermally grown method presented here would facilitate the scalable fabrication of high-quality VO₂thin films and tunable radiative coatings for high-performance thermal control applications.