Nonstoichiometric Oxygen‐Dependent Microstructures and Phase Transitions in Post‐Annealed Vanadium Dioxides

Vanadium dioxide (VO₂) has a metal‐insulator transition (MIT) near room temperature and has attracted considerable interest in both the fundamental science and technological application communities. It is a challenging goal to facilitate a phase transition in complex vanadium oxides by manipulating the stoichiometry. More importantly, the specific hypoxic or hyperoxic microstructure phases simultaneously form when nonstoichiometric oxygen changes in the vanadium dioxides. Here, it is presented that the nonstoichiometric oxygen‐dependent microstructure, bandgap and MITs in post‐annealed VO₂ thin films with V₆O₁₁ and V₆O₁₃ phases at the nanoscale. With an increase in nonstoichiometric oxygen, both the bandgap energies and the phase transition temperatures simultaneously increase. Controlling the hypoxic and hyperoxic states at the nanoscale is an alternative way to explore and manipulate MIT behaviors that depend on the microstructure and composition. It is believed that the dual perspectives help to both understand the underlying physical mechanism of collaborative MITs and construct functional Mott transistors based on multivalent VO₂ thin films.