Variable spin-charge conversion across metal-insulator transition

Photoassisted Electron-Ion Synergic Doping Induced Phase Transition of n-VO2/p-GaN Thin-Film Heterojunction

As a typical correlated metal oxide, vanadium dioxide (VO₂) shows specific metal-insulator transition (MIT) properties and demonstrates great potential applications in ultrafast optoelectronic switch, resistive memory, and neuromorphic devices. Effective control of the MIT process is essential for improving the device performance. In the current study, we have first proposed a photoassisted ion-doping method to modulate the phase transition of the VO₂ layer based on the photovoltaic effect and electron-ion synergic doping in acid solution. Experimental results show that, for the prepared n-VO₂/p-GaN nanojunction, this photoassisted strategy can effectively dope the n-VO₂ layer by H⁺, Al³⁺, or Mg²⁺ ions under light radiation and trigger consecutive insulator-metal-insulator transitions. If combined with standard lithography or electron beam etching processes, selective doping with nanoscale size area can also be achieved. This photoassisted doping method not only shows a facile route for MIT modulation via a doping route under ambient conditions but also supplies some clues for photosensitive detection in the future.

Atomic Origin for Hydrogenation Promoted Bulk Oxygen Vacancies Removal in Vanadium Dioxide

Oxygen vacancies (V_O), a common type of point defect in metal oxides materials, play important roles in the physical and chemical properties. To obtain stoichiometric oxide crystal, the pre-existing V_O is always removed via careful post-annealing treatment at high temperature in an air or oxygen atmosphere. However, the annealing conditions are difficult to control, and the removal of V_O in the bulk phase is restrained because of the high energy barrier of V_O migration. Here, we selected VO₂ crystal film as the model system and developed an alternative annealing treatment aided by controllable hydrogen doping, which can realize effective removal of V_O defects in the VO_2-δ crystal at a lower temperature. This finding is attributed to the hydrogenation accelerated oxygen vacancies recovery in the VO_2-δ crystal. Theoretical calculations revealed that the H-doping-induced electrons are prone to accumulate around the oxygen defects in the VO_2-δ film, which facilitates the diffusion of V_O and thus makes it easier to be removed. The methodology is expected to be applied to other metal oxides for oxygen-related point defects control.