Abstract
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.
| Original language | English |
|---|---|
| Pages (from-to) | 40949-40958 |
| Number of pages | 10 |
| Journal | ACS Applied Materials and Interfaces |
| Volume | 9 |
| Issue number | 46 |
| DOIs | |
| State | Published - Nov 22 2017 |
Funding
The experimental design and planning were sponsored by the Division of Materials Sciences and Engineering, Basic Energy Sciences, Department of Energy (N.B., S.V.K.). The a-IGZO transistor synthesis was supported by NSF grant 1544686 (P.D.R., J.H.N.). The ionic liquid synthesis and device design as well as part of the device characterization was supported by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy (P.Z., S.D.). Part of the device characterization was sponsored by the US Department of Energy (DOE) under Grant No. DOE DE-SC0002136 (A.T.W., P.R.P., T.Z.W.). Molecular dynamics simulations were supported by funding from National Natural Science Foundation of China (51406060) and Natural Science Foundation of Hubei Province of China (2014CFA089) and modeling assistance was provided by S. Li and R. X. Wang (S.B., M.Z., W.Z., G.F.). The necessary measurement protocols for the AFM measurements were developed as part of the Fluid Interface Reactions, Structures, and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (J.M.B., J.C.). The facilities to perform the experiments and the programs to perform data analysis (M.B.O.) were provided by the Center for Nanophase Materials Sciences, which is a DOE office of Science user facility. The experimental design and planning were sponsored by the Division of Materials Sciences and Engineering, Basic Energy Sciences Department of Energy (N.B., S.V.K.). The a-IGZO transistor synthesis was supported by NSF grant 1544686 (P.D.R., J.H.N.). The ionic liquid synthesis and device design as well as part of the device characterization was supported by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle LLC, for the U. S. Department of Energy (P.Z., S.D.). Part of the device characterization was sponsored by the US Department of Energy (DOE) under Grant No. DOE DE-SC0002136 (A.T.W., P.R.P., T.Z.W.). Molecular dynamics simulations were supported by funding from National Natural Science Foundation of China (51406060) and Natural Science Foundation of Hubei Province of China (2014CFA089) and modeling assistance was provided by S. Li and R. X. Wang (S.B., M.Z., W.Z., G.F.). The necessary measurement protocols for the AFM measurements were developed as part of the Fluid Interface Reactions, Structures, and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (J.M.B. J.C.). The facilities to perform the experiments and the programs to perform data analysis (M.B.O.) were provided by the Center for Nanophase Materials Sciences, which is a DOE office of Science user facility.
Keywords
- electric double layer
- ionic liquid
- liquid gating
- scanning probe microscopy
- transistor