Effect of Mo-W Co-doping on semiconductor-metal phase transition temperature of vanadium dioxide film

Molybdenum and tungsten ions were doped into VO2 films by an aqueous sol-gel method. The effect of molybdenum and tungsten co-doping on semiconductor-metal transition of vanadium dioxide films is investigated, and it is compared with single molybdenum doped and undoped films. The composition and microstructure were detected by X-ray photoelectron spectroscopy, X-ray diffraction (XRD) and atomic force microscopy (AFM). The XRD patterns suggest that the prepared films are all strongly (011) oriented on muscovite (001) substrate at room temperature, attributing to the drive to minimize surface energy; and Mo-W codoping does not change the orientation of VO2 film on muscovite (001). It is inferred from the morphology by AFM that codoping induces a smaller grain size and a smoother surface. The infrared transmittance hysteresis cycles prove that codoping lowers phase transition temperature to a larger extent than single Mo doped films at the same doping level, with the change of optical transmittance below and above the phase transition temperature maintained. The positive effect of single molybdenum or tungsten doping on lowering phase transition temperature is enlarged when they were simultaneously added into VO2 films.