Preparation of W-doped VO2/FTO composite thin films by DC magnetron sputtering and characterization analyses of the films

Abstract

In order to obtain low phase transition temperature and superior thermochromic optical material, W-doped VO2/FTO composite thin films are prepared by depositing metallic vanadium on FTO (F:SnO2) conductive glass substrate in argon atmosphere at room temperature and then annealed in air ambient. XPS, XRD and SEM are used for analyzing the structures and surface morphologies of the films. The results indicate that no mixed oxides of V, W and F are produced during high-temperature thermal oxidation. W is doped by replacing V atoms. Compared with the pure VO2/FTO composite thin film prepared using the same process, the crystal orientation of W-doped VO2 thin film is not changed and still retains preferred crystal orientation in the (110) direction. The phase transition temperature drops down to about 35 ℃, and the thermal hysteresis loop narrows to 4 ℃. The variation of IR transmittance between the high temperature and the low temperature reaches 28%. SEM results show that the crystallinity of the thin film is improved significantly, showing smooth, compact and uniform surface morphology. This brings about many new opportunities for optoelectronic devices and industrial production.