Control of (oxygen) stoichiometry of correlated materials by ionic liquid gating

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Ionic liquid (IL) gating is a powerful tool to significantly alter the physical properties of thin films using relatively low voltages and temperatures. Initially insulating oxides like e.g. VO2 and WO3 can be fully and reversibly volume metallized by applying a gate voltage of only 2-3V across the IL. Although it has been proven for various materials that electrochemical processes play an important role in the IL gate-induced effects, the exact mechanisms are still under discussion and numerous contradictory results published. One possible origin underlying these controversial results might be a lack of purity of the experimental conditions which commonly involve ex-situ processes for the IL device preparation. In this project, we aim to perform a true all in-situ/ultra-high vacuum IL gating study to avoid any influence of contamination or degradation effects of sample surface or IL. Using this all in-situ experiment, we intend to investigate in a first step in detail the mechanisms of the IL gate-induced changes, for instance by carefully determining the number of oxygen vacancies created or refilled in the gating process. Then, we will actually utilize IL gating to tune the oxygen content of correlated materials for systematic stoichiometry dependent studies, and possibly even synthesize chemical phases which usually require extreme conditions to be prepared or are not at all stable.