Electrochemically Triggered Metal–Insulator Transition between VO₂ and V₂O₅

Distinct properties of multiple phases of vanadium oxide (VO_x) render this material family attractive for advanced electronic devices, catalysis, and energy storage. In this work, phase boundaries of VO_x are crossed and distinct electronic properties are obtained by electrochemically tuning the oxygen content of VO_x thin films under a wide range of temperatures. Reversible phase transitions between two adjacent VO_x phases, VO₂ and V₂O₅, are obtained. Cathodic biases trigger the phase transition from V₂O₅ to VO₂, accompanied by disappearance of the wide band gap. The transformed phase is stable upon removal of the bias while reversible upon reversal of the electrochemical bias. The kinetics of the phase transition is monitored by tracking the time-dependent response of the X-ray absorption peaks upon the application of a sinusoidal electrical bias. The electrochemically controllable phase transition between VO₂ and V₂O₅ demonstrates the ability to induce major changes in the electronic properties of VO_x by spanning multiple structural phases. This concept is transferable to other multiphase oxides for electronic, magnetic, or electrochemical applications.