State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology (HUST) , Wuhan 430074, China.
ACS Appl Mater Interfaces. 2017 Nov 22;9(46):40949-40958. doi: 10.1021/acsami.7b11044. Epub 2017 Nov 7.
Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal-insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment and theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.
离子液体门控过渡金属氧化物实现了新的状态（磁性、电子、金属-绝缘体），为强关联氧化物的物理性质提供了基本的见解。然而，尽管研究活动很多，但对于与过渡金属氧化物表面接触的液体的结构、其随外加电场的演变及其与氧化物电子性质的相关性，人们知之甚少。在这里，我们使用实验和理论研究了在薄膜晶体管中，电双层门控器件运行时，离子液体在半导体氧化物界面上的结构。我们表明，非晶铟镓锌氧化物晶体管的 ON 和 OFF 状态之间的转变伴随着氧化物沟道表面上的反离子的致密化和优先空间取向。这个过程发生在三个不同的步骤中，对应于离子取向，因此，也对应于不同电导率的区域。当存在不同的离子排列时，这可以在氧化物表面的表面电荷密度中找到原因。总的来说，场效应门控过程是根据界面离子液体结构来阐明的，这为液体门控晶体管的工作提供了前所未有的见解，将纳米级结构与功能性质联系起来。这种知识将使新型离子液体设计和先进的器件概念成为可能。
