High infrared reflectance modulation in VO2 films synthesized on glass and ITO coated glass substrates using atmospheric oxidation of vanadium

Vanadium Dioxide (VO2) is a strongly correlated material, which exhibits insulator to metal transition at similar to 68 degrees C along with large resistivity and infrared optical reflectance modulation. In this work, we use atmospheric pressure thermal oxidation of Vanadium to synthesize VO2 films on glass and ITO coated glass substrates. With the optimized short oxidation durations of 2 min and 4 min, the synthesized VO2 film shows high optical reflectance switching in long-wavelength infrared (8-14 mu m) on glass substrates and mid-wavelength infrared (3-5 mu m) on ITO coated glass substrates, respectively. Peak reflectance switching values of similar to 76% (at 9 mu m) and similar to 79% (at 4.6 mu m.) are obtained on the respective substrates, which are among the highest reported values. Using the reflectance data, we extract VO2 complex refractive index in infrared wavelengths, in both the insulating and metallic phases. The extracted refractive index shows good agreement with VO2 synthesized using other methods. This demonstration of high optical reflectance switching in VO2 thin films, grown on low cost glass and ITO coated glass substrates, using a simple low thermal budget process will aid in enhancing VO2 applications in the optical domain.