Defect-Superstructure-Engineered Vanadium Dioxide Films for Electric-Field-Driven Phase Reconfiguration and Overload Protection

Electric-field-induced phase switching in vanadium dioxide (VO₂) is central to its integration into adaptive electronic systems. However, the role of oxygen defects in governing structural stability and switching behavior remains insufficiently understood. Here, we engineer oxygen-deficient VO₂ (VO_2-δ) films to investigate the structure of VO_2-δ and the electrical switching behavior systematically. The preferential occupation of oxygen vacancies was identified, which induces a 3-fold superstructure of (011)_R and stacking faults with a certain degree of long-range ordering along (110)_R and (020)_R. Even so, the VO_2-δ maintains the rutile-like coordination structure as VO₂. Notably, the VO_2-δ films exhibit high conductivity at room temperature. An irreversible metal–insulator transition can be triggered at 20 V for the VO_2-δ film, enabled by localized Joule-heating-assisted reorganization of the oxygen-vacancy defect structure. The resulting abrupt resistance jump highlights the potential of VO_2-δ as an ultrathin active medium for fast electronic overload protection. This work establishes vacancy ordering as a powerful lever for tailoring phase behavior in VO₂, offering a defect-engineering pathway toward reconfigurable oxide electronic devices.