Insulator to metal transition in WO3 induced by electrolyte gating

Abstract

Electrolyte gating: Hydrogenation mechanism in WO3 The mechanism leading to large carrier density changes and even concomitant electronic phase transitions with electrolyte gating is under debate. An international team led by Ivan Božović at USA’s Brookhaven National Laboratory and Yale University report a series of experiments based on WO3 films, which is found to exhibit an insultator-to-metal transition under gating, with both ionic liquids and polymer electrolytes. The experimental results allow to rule out some mechanisms—such as charge accumulation near the interface or oxygen vacancy formation—previously suggested in other material systems. Instead, the authors propose that the primary effect of electrolyte gating in WO3 is hydrogen intercalation. Hydrogenation leads to the formation of a dense polaronic gas that explains the conductive ground state. The doping mechanism behind electrolyte gating seems to be material dependent.