Effect of vacuum on preparation and optical and electrical properties of VO2(B) film

The structure, valence, electrical properties and optical properties of the VO2(B) thin films are analysed and measured to study the effect of annealing vacuum on the thin films. The VO2 thin films are deposited by vacuum-evaporation technology using the V2O5 powder (purity99.99%, in mass) as raw material. The V2O5 thin films are annealed at high and low vacuum in the vacuum coating machine, respectively. The space group of the obtained VO2(B) thin films is C2/m. The thin films are measured by X-ray diffraction (XRD), X-ray photo-electron spectrum (XPS), temperature coefficient resistance (TCR) instrument and ultraviolet-visible spectrophotometer. The results suggest that the temperature range of the VO2(B) thin films gained is different. The range is from 400C to 480C when the film is annealed in low vacuum, and it was only from 400C to 440C when the film is annealed in high vacuum. The crystal sizes change bigger and the transmission of the thin films annealed in the high vacuum is 7%-8% bigger than that annealed in low vacuum, but the vanadium's valence of the thin films are lower and the TCR's absolute value of the films are bigger which is up to -2.4%/K when annealed in low vacuum.