Self-Organization of Ions at the Interface between Graphene and Ionic Liquid DEME-TFSI

Guangliang Hu; Gaind P Pandey; Qingfeng Liu; Radhika S Anaredy; Chunrui Ma; Ming Liu; Jun Li; Scott K Shaw; Judy Wu

doi:10.1021/acsami.7b10912

Self-Organization of Ions at the Interface between Graphene and Ionic Liquid DEME-TFSI

ACS Appl Mater Interfaces. 2017 Oct 11;9(40):35437-35443. doi: 10.1021/acsami.7b10912. Epub 2017 Sep 25.

Authors

Guangliang Hu^{1

2

3}, Gaind P Pandey⁴, Qingfeng Liu³, Radhika S Anaredy⁵, Chunrui Ma¹, Ming Liu², Jun Li⁴, Scott K Shaw⁵, Judy Wu³

Affiliations

¹ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China.
² School of Microelectronics, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, China.
³ Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States.
⁴ Department of Chemistry, Kansas State University , Manhattan, Kansas 66506, United States.
⁵ Department of Chemistry, University of Iowa , Iowa City, Iowa 52242, United States.

PMID: 28920423
DOI: 10.1021/acsami.7b10912

Abstract

Electrochemical effects manifest as nonlinear responses to an applied electric field in electrochemical devices, and are linked intimately to the molecular orientation of ions in the electric double layer (EDL). Herein, we probe the origin of the electrochemical effect using a double-gate graphene field effect transistor (GFET) of ionic liquid N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethylsulfonyl)imide (DEME-TFSI) top-gate, paired with a ferroelectric Pb_0.92La_0.08Zr_0.52Ti_0.48O₃ (PLZT) back-gate of compatible gating efficiency. The orientation of the interfacial molecular ions can be extracted by measuring the GFET Dirac point shift, and their dynamic response to ultraviolet-visible light and a gate electric field was quantified. We have observed that the strong electrochemical effect is due to the TFSI anions self-organizing on a treated GFET surface. Moreover, a reversible order-disorder transition of TFSI anions self-organized on the GFET surface can be triggered by illuminating the interface with ultraviolet-visible light, revealing that it is a useful method to control the surface ion configuration and the overall performance of the device.

Keywords: electrochemical effect; graphene field effect transistor; interface; ionic liquid; self-organization.