The effect of vacuum preheating on the structure, electric, and optical properties of W-doped VO2 films prepared from thermal oxidation

Abstract

The effect of vacuum preheating on the structure, electric, and optical properties of the thermally oxidized W-doped VO2 films was studied. The results show that the film crystalline orientation and the inhomogeneous distribution of W increase after preheating. It was found that preheating at 700 °C and 800 °C reduces the metal-insulator transition (MIT) hysteresis because of the preferable orientation of the film along the (011) direction. The film preheated at 900 °C exhibits an undoped-like MIT due to a great increase in the inhomogeneous distribution of W. Preheating can affect the apparent activation energy of the cool-state resistances and increase the cool-state IR transmittances. By means of the Lorentz–Drude model, the conductance electron density (n c) and energy band gaps (E g) were obtained and discussed. It was shown that preheating can decrease the cool-state n c and affect the E g, indicating that the electronic band structure is changed by W doping.