Large change of visible transmittance with VO2 phase transition in VO2/TiO2 polycrystalline films

• The TiO2 layer increases the visible transmittance of SiO2/VO2/TiO2 structure.
• The transmittance changes largely with VO2 phase transition at λ = 580–770 nm.
• The large transmittance change offers another freedom to design infrared detectors.

The transmittance at the wavelength (λ) of 580–770 nm greatly changes when the semiconducting VO2 phase transforms to the metal phase in TiO2/VO2 films grown on (0001) SiO2 substrate. The ~ 180 nm TiO2 layer as the antireflective coating enhances the transmittance of semiconducting VO2 film to ~ 48% at λ = 630 nm at 20 °C. When the temperature rises to 85 °C, the evolution of refractive index (n and k) of VO2 film allows a largely enhanced reflectivity and absorptance, which decreases the transmittance of metal VO2 film to ~ 30% at λ = 630 nm. The ~ 18% transmittance change with the phase transition is much higher than that in single VO2 film and is helpful to design high-resolution infrared detectors at room temperature.