Transition-metal oxides exhibit various potentially useful electronic properties. Among them, vanadium dioxide (VO2) is of great interest due to the potential application of its prominent properties. It undergoes a metal–insulator transition (MIT) accompanied by a structural change from high-temperature tetragonal to low-temperature monoclinic phases above room temperature. Dimerization of V ions to form spin singlet state opens the gap in the insulating phase, which causes a sharp resistivity jump at the transition temperature. Therefore, numbers of studies have been performed to realize switching devices or sensors operating at room temperature.
I will present the effects of epitaxial strain on MIT in VO2 films on TiO2, MgF2, and Al2O3 substrates. The transition temperature is systematically changed due to the variation of in-plane lattice constants of VO2 films. The transition temperature is also controlled by impurity doping and external stimuli. I will show the phase stability of VO2 on Si substrate for integrating this material with Si-based devices. If time permits, I will also report our recent studies on VO2-based device application.