Large Transport Gap Modulation in Graphene via Electric Field Controlled Reversible Hydrogenation

TL;DR

This paper demonstrates a reversible, electric field-controlled hydrogenation process in graphene that significantly modulates its transport gap, enabling high on/off ratios and durable switching in graphene transistors.

Contribution

It introduces a novel electrochemical method to reversibly control graphene's conductivity via hydrogenation, enhancing transistor performance.

Findings

Achieved on/off ratios of 10^8 at room temperature.

Demonstrated high endurance with up to one million switching cycles.

Reversible hydrogenation modulates the transport gap in graphene.

Abstract

Graphene is of interest in the development of next-generation electronics due to its high electron mobility, flexibility and stability. However, graphene transistors have poor on/off current ratios because of the absence of a bandgap. One approach to introduce an energy gap is to use hydrogenation reaction, which changes graphene into insulating graphane with sp3 bonding. Here we show that an electric field can be used to control conductor-to-insulator transitions in microscale graphene via a reversible electrochemical hydrogenation in an organic liquid electrolyte containing dissociative hydrogen ions. The fully hydrogenated graphene exhibits a lower limit sheet resistance of 200 Gohm/sq, resulting in graphene field-effect transistors with on/off current ratios of 10^8 at room temperature. The devices also exhibit high endurance, with up to one million switching cycles. Similar insulating behaviours are also observed in bilayer graphene, while trilayer graphene remains highly conductive after the hydrogenation. Changes in the graphene lattice, and the transformation from sp2 to sp3 hybridization, is confirmed by in-situ Raman spectroscopy, supported by first-principles calculations.