Role of buffer layers on the strain-induced insulator-metal transition of VO ₂ thin films: a review

Vanadium oxide (VO2) is a strongly correlated material that undergoes an insulator to metal transition at around 68 °C. Unlike other vanadium oxides, VO2 shows phase transition behavior near room temperature, making it an appropriate candidate material for different applications such as thermochromic devices, microwave tunable devices, memory devices, etc. Many practical applications necessitate further tuning of the phase transition temperature to make it more adaptable, either below or above 68 °C. This adaptability is crucial for device efficiency and versatility. The phase transition behavior can be changed by various techniques, including light irradiation, lattice strain modulation, external electric field, and higher and lower valence elements doping. Strain variation is a widely used strategy in the aforementioned methods, and it is achieved by either using suitable substrates or incorporating appropriate buffer layers. This article reviews the various buffer layers used in VO2 thin films and their role in the insulator-metal transition behavior and thermochromic properties, highlighting their significance in enhancing the material’s performance in various applications.