Metal-graphene heterojunction modulation via H2 interaction

Abstract

Combining experiment and theory, we investigate how a naturally created heterojunction (pn junction) at a graphene and metallic contact interface is modulated via interaction with molecular hydrogen (H2). Due to an electrostatic interaction, metallic electrodes induce pn junctions in graphene, leading to an asymmetrical resistance in electronic transport for electrons and holes. We report that the asymmetry in the resistance can be tuned in a reversible manner by exposing graphene devices to H2. The interaction between the H2 and graphene occurs solely at the graphene-contact pn junction and induces a modification on the electrostatic interaction between graphene and metallic contacts. We explain the experimental data with theory providing information concerning the length of the heterojunction and how it changes as a function of H2 adsorption. Our results are valuable for understanding the nature of the metal-graphene interfaces and have potential application for selective sensors of molecular hydrogen.