Microstructures and thermochromic characteristics of low-cost vanadium–tungsten co-sputtered thin films

Tungsten–vanadium (W–V) co-sputtered thin films at a low cost were successfully synthesized on glass substrates by magnetron sputtering at room temperature and annealing under air atmosphere. The microstructures and optical properties of the thin films were characterized by four approaches, such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and spectrophotometer. XPS analysis demonstrated that W–V co-sputtered thin films were mostly composed of VO2 and W6 +, with a little amount of V2O5 and other tungstovanadic compounds. XRD patterns illustrated that W–V co-sputtered thin films were polycrystal and W–V co-sputtered approach did not change the preferred orientation growth of the thin films. SEM micrographs displayed that VO2 thin films were irregular in shape and distributed randomly, while W–V co-sputtered thin films had a rod-like morphology. Spectrophotometer spectra showed that W–V co-sputtered approach decreased the phase transition temperature from 68 °C to 40 °C, narrowed the thermal hysteresis loop from 6 °C to 3 °C, and made little influence on the infrared transmittance of pure VO2 thin films.