High substrate temperature induced anomalous phase transition temperature shift in sputtered VO2 thin films

Vanadium dioxide (VO2) thin films were deposited onto Corning glass substrates by rf reactive inverted cylindrical magnetron sputtering at different substrate temperatures (Ts) ranging from 450 to 600 °C. The influence of substrate temperature on the structural and optical properties was systematically investigated. It revealed that the crystallinity of the VO2 films improved significantly with Ts. The substrate temperature to obtain films with transition temperature (Tc ∼ 70 °C) similar to VO2 bulk single crystal was 450–500 °C, while high substrate temperatures from 550 to 600 °C tend to shift Tc towards higher temperatures from 75 to 80 °C keeping the sharpness of the transition unaltered. Even if the variation of the Tc of VO2 is not dramatic “variation from 70 to 80 °C” with increasing Ts is substantial for undoped VO2 thin films. This sizeable variation of ∼10 °C confirms the tunability of the Tc of VO2 through Ts.