Electrolyte Gating of Two-Dimensional Electron Gas at Oxide Interfaces

We demonstrate the modulation of electrical transport properties in both crystalline and amorphous LAO/STO interfaces by electric field effect using electric double layer transistor (EDLT) configuration. For the crystalline LAO/STO interfaces, reversible metallic-insulating phase transition and field-effect transistor operation are observed, which indicates that the carriers in the interfaces could be reversible accumulated and depleted. Moreover, enhancement of mobility and the resultant quantum oscillations of the conductance due to the depletion of carrier density are obtained. For the amorphous LAO/STO interfaces in which the conductivity is caused by oxygen vacancy formation, it is found that filling of oxygen vacancies and therefore, the decrease in carrier density after liquid gating, suggesting the presence of oxygen migration. The filling effect causes the reconstruction of interfacial band structures, that can be controlled by the LAO overlayer deposition temperature, suggesting a method for tuning the band structures and oxidation states of buried interfaces.