Ionic liquid gate induced modifications of oxides surface*

Intense electric fields developed during gating at the interface between an ionic liquid (IL) and an oxide layer have been shown to lead to significant structural and electronic phase transitions in the entire oxide layer. An archetypical exampleis the reversible transformation between the brownmillerite SrCoO_2.5 and the perovskite SrCoO₃ engendered by ionic liquid gating. In this presentation, we show using in-situ atomic force microscopy studies, with photothermal excitation that allows for high quality measurements in the viscous environment of the ionic liquid, that the edges of atomically smooth terraces at the surface of SrCoO_2.5 films are significantly modified by IL gating but that the terraces themselves remain smooth. The edges develop ridges that we show, using complementary X-ray photo emission spectroscopy studies, result from the adsorption of hydroxyl groups. Our findings open up opportunities for electrically controlled surface modifications in emergent ionitronic applications.