Tunability of the Metal–Insulator Transition in VO₂/TiO₂ Heterostructures

The metal–insulator transition in strongly correlated vanadium dioxide (VO₂) has attracted considerable interest. It has been shown that formation of oxygen vacancies (V_O) in VO₂ can suppress this MIT completely without any structural transition. Since V_O can be introduced via tuning the thickness or type of capping oxide layers, in this work, we studied the control of MIT in VO₂ by interfacing with a TiO₂ capping layer. Using a combined approach with experimental measurements and theoretical calculations, we find that a TiO₂ capping layer on an epitaxial VO₂ thin film suppresses the MIT in VO₂. Density functional theory (DFT) calculations, benchmarked against more accurate many-body quantum Monte Carlo (QMC) calculations, provide information on the V_O formation energy profile across the VO₂/TiO₂ interface. It is found that the VO₂/TiO₂ interface can facilitate the V_O migration from TiO₂ to VO₂, and it is this migration that is responsible for the suppression of MIT in VO₂. Our study highlights the crucial role of V_O introduced by a capping layer in tuning the MIT in epitaxial VO₂ thin films, which is useful for developing advanced electronic and iontronic devices.