Study on optical and electrical switching properties and phase transition mechanism of Mo⁶⁺-doped vanadium dioxide thin films

Abstract

In the present work using V₂O₅ and MoO₃ powders as precursors, a novel method, the inorganic sol-gel method, was developed to synthesize Mo⁶⁺ doped vanadium dioxide (VO₂) thin films. The structure, valence state, phase transition temperature, magnitude of resistivity change and change in optical transmittance below and above the phase transition of these films are determined by XRD, XPS, four-point probe equipment and spectrophotometer. The results showed that the main chemical composition of the films was VO₂, the structure of MoO₃ in the films didn't change, and the phase transition temperature of the VO₂ was obviously lowered with increasing MoO₃ doped concentration. The magnitude of resistivity change and change in optical transmittance below and above phase transition were also decreased, of which the magnitude of resistivity change was more distinct. However, when the MoO₃ concentration was 5 wt%, the magnitude of resistivity change of doped thin films still reached more than 2 orders, and the change in optical transmittance below and above phase transition was maintained. Analysis showed that the VO₂ doped films formed local energy level, and then reduced the forbidden band gap of VO₂ as the donor defect changing its optical and electrical properties and lowering the phase transition temperature.