A facile method for the preparation of W-doped VO₂ films with lowered phase transition temperature, narrowed hysteresis loops and excellent cycle stability

We present a facile method to prepare W - doped VO₂ films with lowered phase transition temperature (T_t), narrowed hysteresis loops width (ΔT_t) and excellent cycle stability. The W - doped VO₂ films have been obtained by inorganic sol - gel method. And W dopant is introduced by pouring melt V₂O₅ into ammonium tungstate solution. The properties of the samples are measured by XRD, XPS, SEM and transmittance spectra. The T_t is reduced from 73 °C to 20 °C along with the ΔT_t narrowed from 10 °C to 4 °C as W dopant increasing from 0 to 3.2 at%. Besides, no obvious attenuation is observed on crystal structure, variation of transmittance (ΔT_2000nm), T_t and ΔT_t for W - doped VO₂ films after 550 alternate heating and cooling cycles, while the pure VO₂ films show obvious degradation. Since the surface morphology has no obvious changes after 550 cycles, it suggests that the W dopant induced distorted crystal structure strengthen the cycle stability of W - doped VO₂ films. These encouraging results show great potential and understanding of VO₂ films for practical applications.