Electric Double Layer Dynamics in Poly(ethylene oxide) LiClO₄ on Graphene Transistors

Abstract

Formation of an electric double layer (EDL) is a powerful approach for exploring the electronic properties of two-dimensional (2D) materials because of the ultrahigh capacitance and induced charge in the 2D materials. In this work, epitaxial graphene Hall bar devices are gated with an EDL using a 1 μm thick solid polymer electrolyte, poly­(ethylene oxide) and LiClO4. In addition to carrier density and mobility, ion dynamics associated with the formation and dissipation of the EDL are measured as a function of temperature over a gate bias range of ±2 V. The room temperature EDL formation time (∼1–100 s) is longer than the dissipation time (∼10 ms). The EDL dissipation is modeled by a stretched exponential decay, and the temperature-dependent dissipation times are described by the Vogel–Fulcher–Tammann equation, reflecting the coupling between polymer and ion mobility. At low temperatures, approaching the glass transition temperature of the electrolyte, the dissipation times of both cations and anions exceed several hours, and both p- and n-type EDLs can persist in the absence of a gate bias. The measured temperature-dependent relaxation times qualitatively agree with COMSOL multiphysics simulations of time-dependent ion transport in the presence of an applied field.

Impact of Post‐Lithography Polymer Residue on the Electrical Characteristics of MoS2 and WSe2 Field Effect Transistors

“…Electrolyte Preparation and EDL‐Gating Experiments : The polymer electrolyte preparation process was similar to previously published results . PEO:CsClO 4 was prepared inside an argon‐filled glove box with H 2 O and O 2 concentration < 0.1 parts‐per‐million (ppm).…”

Silver Nanofilament Formation Dynamics in a Polymer‐Ionic Liquid Thin Film by Direct Write

“…One clue regarding the contribution of the IL comes from their use as high-capacitance gate dielectrics in electrolyte-gated transistors. [26] Up to half of the applied potential can drop across the EDL [27,28] (depending on the ion concentration and the geometry of the electrodes) leaving relatively little drop in the bulk of the electrolyte to drive ion migration. Specifically, when a positive bias is applied to the anode, cations drift to the cathode surface forming an EDL at the interface between the electrolyte and the cathode and induce an image charge in the electrode that is detected as a charging current.…”

Ion-Locking in Solid Polymer Electrolytes for Reconfigurable Gateless Lateral Graphene p-n Junctions

“…Similar to metal gates, electric double layer (EDL) gating is an electrostatic approach; however, EDL gating involves positioning ions at the interface between an electrolyte and a 2D surface by field effect. The ions induce image charge in the channel, and can achieve doping densities > 10 13 cm −2 because of the < nm charge separation distance between ions and image charges [28][29][30][31][32][33][34][35][36]. Because this approach does not rely on replacing atoms in the 2D crystal or transferring charge, this method avoids permanently changing the crystal structure and potential problems associated with doping defects.…”