Ionic Liquid Gating Control of Oxygen Vacancies in the La0.8Ba0.2MnO3 Ultrathin Films

In this work, we show ionic liquid field-effect of La 0.8 Ba 0.2 MnO 3 (LBMO) untrathin films prepared by the sol-gel method. When applying a positive gate voltage ( V g ) in vacuum, it is found that the film resistivity continuously increases tenfold within hours or minutes depending on the magnitude of V g , accompanied with disappearance of the low-temperature metallic transport behavior. In contrast, the film resistivity changes little in air or under a negative applied V g . Such a difference reveals that the increased resistivity is related to the oxygen depletion in the films under the positive V g , especially at the grain boundaries. After removing the positive V g in vacuum, the room-temperature resistivity begins to fall off and the low-temperature metallic state is partially restored in several tens hours, suggesting oxygen diffusion from the relatively oxygen-rich grains to the seriously oxygen-deficient grain boundaries. Furthermore, the oxygen content in the oxygen-deficient films can be almost fully restored in ten minutes by external annealing (200 °C) or Joule self-heating (21 mA) the films in air. These experimental findings provide an additional method in tuning oxygen vacancies in transition-metal oxide films.