Oxygen defect engineering of the metal–insulator transition and nanoscale percolation in VO2 films

This study investigates the modulation of the metal–insulator transition (MIT) in magnetron-sputtered VO2 films via oxygen defect engineering. At an optimal oxygen flow of 0.6 SCCM, the films exhibit a sharp MIT with a resistance modulation exceeding three orders of magnitude and a narrow thermal hysteresis of 8.8 °C. Using in situ temperature-dependent conductive atomic force microscopy, the nanoscale evolution of local percolation channels governed by oxygen vacancies is directly visualized. The results demonstrate that an oxygen-rich environment induces microscopic defects and reshapes the percolation network, thereby reducing the insulating-state resistance and broadening the phase-transition temperature range. As the temperature rises, thermally excited carriers overcome local confinement, forming a globally connected metallic network during the transition. This work establishes a profound correlation between nanoscale defect dynamics and macroscopic electrical properties, providing crucial insights for VO2-based memristors and related micro/nanoelectronic devices.