Electrolyte gate controlled metal-insulator transitions of the CaZrO3/SrTiO3 heterointerface

Two-dimensional electron gas (2DEG) at a complex oxide interface shows an extraordinary spectrum of intriguing phenomena and functionality. Another oxide 2DEG was recently created via strain-induced polarization at an otherwise nonpolar perovskite-type interface of CaZrO3/SrTiO3 (CZO/STO). Herein, we report an effective way to tune the CZO/STO interface via ionic liquid (IL) electrolyte gating. An unexpected metal-insulator transition of the interfacial 2DEG occurs readily with the immersion of the sample in an IL even before the gate voltage is applied. This suggests the presence of intrinsic polarization of CZO, which could act as a negative bias. The carrier density is found to be suppressed and shows a temperature-independent behavior after electrolyte gating which also resulted in higher electron mobility. These results suggest that the oxygen vacancies are annihilated via oxygen electromigration to the interface induced by electrolyte gating. The effective tunability by IL gating shed more light on the mechanism of electrolyte gating on the buried heterointerface.