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Unique Constant Phase Element Behavior of the Electrolyte–Graphene Interface

Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA
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Nanomaterials 2019, 9(7), 923; https://doi.org/10.3390/nano9070923
Received: 6 May 2019 / Revised: 23 May 2019 / Accepted: 29 May 2019 / Published: 27 June 2019
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Abstract

We report a unique constant phase element (CPE) behavior ( 1 Z = Q 0 ( j ω ) α ) of the electrolyte–graphene interface with both Q 0 and α showing dependence on the gate voltage. The frequency response of the electrolyte–graphene interface was studied using electrochemical impedance spectroscopy (EIS). The result suggests that (1) the electrolyte–graphene interface should be characterized as a CPE ( α < 1), rather than an ideal capacitor; and (2) both Q 0 and α show ambipolar dependence on the applied voltage. We speculate that the CPE behavior of the electrolyte–graphene interface arises from the charged impurities on the substrate and the defects in the graphene lattice, which could introduce inhomogeneity of local density of states (DOS). The low density of states of graphene makes α sensitive to these local DOS near the Dirac point, and thus showing dependence on the gate voltage. Measurement of the electrolyte–graphene interface capacitance based on multi-frequency capacitance-voltage (CV) profiling was demonstrated, and the extraction of the carrier mobility was performed. The study could lead to a more accurate understanding of the capacitive behavior of the electrolyte–graphene interface, which is instructive for the design and analysis of devices involving the electrolyte–graphene interface for nanoelectronics and bioelectronics applications. View Full-Text
Keywords: electrolyte–graphene interface; constant phase element; frequency response electrolyte–graphene interface; constant phase element; frequency response
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Sun, J.; Liu, Y. Unique Constant Phase Element Behavior of the Electrolyte–Graphene Interface. Nanomaterials 2019, 9, 923.

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