Microstructures and thermochromic properties of tungsten doped vanadium oxide film prepared by using VOX–W–VOX sandwich structure

Tungsten doped vanadium oxide (VOX) thin films were prepared by oxygen annealing VOX–W–VOX sandwich layers. X-ray photoelectron spectroscopy, X-ray diffraction and field emission scanning electron microscope were employed to characterize the compositions, crystal structures and surface morphologies, respectively. It was demonstrated that sandwich structure suppressed the crystallization of VOX, and that V5+ was reduced by diffused W atom to V4+. The results of surface morphologies indicated that the grain arrangement of W doped vanadium dioxide film exhibited some regular patterns compared with the random grain distribution of undoped film. Electrical measurements showed that the square resistance of V2O5 film and semiconductor-metal transition temperature of VO2–V2O5 film decreased obviously after W doping. In addition, thermal hysteresis loop was observed in W doped V2O5 film with thick W middle layer. The investigation of optical properties indicated that the optical band gap of W doped V2O5 film decreased with the increase of thickness of W middle layer, and the optical switching performance in the near-infrared range of VO2–V2O5 slightly weakened after W doping.