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

离子液体(IL)门控是一种强大的工具，可以在相对较低的电压和温度下显著改变薄膜的物理性质。最初，只需在IL上施加2-3V的栅极电压，就可以完全和可逆地对VO2和WO3等绝缘氧化物进行体积金属化。尽管各种材料已经证明了电化学过程在IL-Gate诱导效应中起着重要作用，但确切的机制仍在讨论中，并公布了许多相互矛盾的结果。这些有争议的结果背后的一个可能的根源可能是缺乏实验条件的纯度，这些实验条件通常涉及用于IL装置准备的异地过程。在这个项目中，我们的目标是进行真正的全原位/超高真空离子注入门控研究，以避免样品表面或离子注入的污染或降解效应的任何影响。利用这一全原位实验，我们打算在第一步详细研究IL门诱导的变化的机制，例如通过仔细确定在门控过程中产生或重新填充的氧空位的数量。然后，我们实际上将利用IL GATING来调节相关材料的氧含量，以进行系统的化学计量比依赖研究，甚至可能合成通常需要极端条件才能制备或根本不稳定的化学相。

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.