Insight into Electronic and Structural Reorganizations for Defect-Induced VO₂ Metal-Insulator Transition

An oxygen vacancy defect in monoclinic VO₂ has been shown to modulate the metal-insulator transition (MIT) at room temperature. However, as the electronic and structural reorganizations occur simultaneously, the origin of MIT is still unclear. Here we performed first-principles calculations to examine electronic variations separately from structural reorganizations during MIT. It was found that the oxygen defect induces electronic reorganization by creating polarized 3d orbitial electrons, while structure reorganization makes the conduction band edge states available for occupation. The conduction band states thus hold polarized charges that delocalize over space, bestowing metallic property on the originally insulated VO₂. A linear relationship for the number of polarized electrons and the defect concentration is revealed, which would lead to cost-effective control of VO₂ MIT behavior by defect engineering.