Metal-Insulator Transition Detection of Vanadium Dioxide Thin Films by Visible Light Reflection

Vanadium dioxide (VO₂)-based thin films have received considerable attention in recent years due to their superior performance in creating next-generation color-rendering materials. The near-room-temperature metal-insulator transition of VO₂ promises the advantage of active color tuning in the visible wavelength range. Although various results of dynamic color generation combined with plasmonic nanostructures are currently being investigated, so far, very few studies have addressed the visible-light optical performance of pure VO₂ thin films prepared on conventional substrates. This article shows in detail the phase-transition behavior of VO₂ thin films in the visible wavelength range of 400-750 nm prepared on glass with subsequent annealing at temperatures of 350, 400, 450, and 500 °C. The results show an anomalous phase transition reducing the overall RGB reflectivity correlated with the crystallization behavior of the VO₂ phase and scattering effect. The sample annealed at 350 °C shows the smallest phase transition at 47 °C, correlating with a crystallite size of 7 nm. The blue band reflectivity anomaly after annealing at 450 °C was considered an effect of the secondary reflection. The results of this research could play a huge role in the production of active-switching photonic devices, color-managed reflectors, and temperature indicators.