Tafel-Kinetics-Controlled High-Speed Switching in a Electrochemical Graphene Field-Effect Transistor

Abstract

Graphene field-effect transistors (FETs) have attracted tremendous attention owing to the single-atomic-layer thickness and high electron mobility for potential applications in next-generation electronics. With regards to switching methodology, the electric-field-induced metal−insulator transition offers a new strategy to produce a large on/off current ratio through reversible electrochemical hydrogenation of the graphene channels. Therefore, the performance of such electrochemical graphene FETs greatly relies on the kinetics of hydrogenation reaction. Here, we show that the switching time can be systemically controlled by the applied gate voltages and geometries of graphene channels. The turn-on and turn-off time display an exponential dependence on the gate voltages, manifesting the dominated Tafel-form kinetics of hydrogenation reaction in a two-dimensional limit. Moreover, the turn-off time is inversely proportional to the channel width but independent of the length, while the turn-on time relies on both the width and length, as well as the off-state gate voltage and duration. Our work improves the response time to the magnitude of tens of microseconds and advances the application of graphene-based electronic devices.

Gate-Controlled Neuromorphic Functional Transition in an Electrochemical Graphene Transistor

“…For devices used in Raman spectroscopy measurements, a long strip of platinum foil was used as the gate electrode instead. The detailed assembly procedures and electrolyte injection were reported in our previous works. , The hydrogen ion electrolyte consisted of 0.4 mol/L bis­(trifluoromethane)­sulfonamide (HTFSI) in liquid poly­(ethylene glycol) (PEG) with an average M n of 600. The PEG was heated to 100 °C for a few hours followed by vacuum evacuation to remove residual moisture.…”

“…When V G returns to −1 V, the graphene is dehydrogenated, and I DS promptly recovers back to the LRS. Notably, our previous work has demonstrated that such an on/off ratio can reach 10 8 with high reversibility for ≤1 million switching cycles, , which presents exciting implications for the development of advanced devices that require high stability and specificity through the delicate control of C–H bond concentration in graphene.…”

“…When V G is restricted within the range of −1.0 to 1.5 V, the characteristic V-shaped behavior in this curve originates from the linear dispersion of relativistic Dirac Fermions in pristine graphene, , defined as a low-resistance state (LRS) in our experiments. However, as the gate voltage exceeds the hydrogenation voltage ( V H ), which is ∼1.8 V, the H + ions accumulating on the top of the graphene surface start to react with the graphene, causing a change in the hybridization of the carbon atom from sp 2 to sp 3 , which then localizes the conduction electrons and switches to the high-resistance state (HRS). − This results in a sharp decrease in I DS to nearly zero. When V G returns to −1 V, the graphene is dehydrogenated, and I DS promptly recovers back to the LRS.…”