Multi-state structural modulation of hydrogenated VO₂ revealed by in situ x-ray diffraction

The generation and control of multiple phases via hydrogen insertion open up avenues for tuning the properties of transition metal oxides. Here, by employing both in situ x-ray diffractions and in situ electrical measurements, we accurately probed the full structural phase transitions during the reversible process of hydrogen insertion into and extraction from the vanadium dioxide lattice. Repeatable switches between the hydrogenated VO2 phases and the pristine VO2 phase were demonstrated, implying potential applications for hydrogen detection/storage and multi-state information memorizers. Moreover, different phases were further discussed by synchrotron x-ray absorption spectroscopy and theoretical first-principles calculations, which reveal that hydrogen insertion greatly affects the filling of the d-band as well as the electrical properties. This work will provide fundamental insight into the comprehensive understanding of hydrogen-induced phase transition in metal oxides and may guide the development of proton-based sensors and devices.