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

Pristine vanadium dioxide (VO 2 ), an insulator-to-metal transition (IMT) material, is grown via furnace oxidation followed by rapid thermal annealing with forming gas (5% H 2 /95% N 2 ) which reduces surface over-oxides such as V 2 O 5 formed 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 VO 2, 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 VO 2 thin 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 VO 2 prepared by other sophisticated fabrication techniques. The thermally grown method presented here would facilitate the scalable fabrication of high-quality VO 2 thin films and tunable radiative coatings for high-performance thermal control applications.