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.