Carrier density modulation in graphene underneath Ni electrode

TL;DR

This study examines whether the carrier density in graphene beneath Ni electrodes in FETs is fixed or modulated, finding that the electrical properties are largely unaffected by contact, likely due to interface residuals.

Contribution

It reveals that the carrier density in graphene under Ni electrodes remains modulated by the back-gate, challenging the assumption of fixed carrier density at contacts.

Findings

Graphene's resistance shows back-gate dependence under Ni electrodes.

Residual resist at the interface reduces metal-graphene interaction.

Carrier density modulation persists underneath Ni contacts.

Abstract

We investigate the transport properties of graphene underneath metal to reveal whether the carrier density in graphene underneath source/drain electrodes in graphene field-effect transistors is fixed. The resistance of the graphene/Ni double-layered structure has shown a graphene-like back-gate bias dependence. In other words, the electrical properties of graphene are not significantly affected by its contact with Ni. This unexpected result may be ascribed to resist residuals at the metal/graphene interface, which may reduce the interaction between graphene and metals. In a back-gate device fabricated using the conventional lithography technique with an organic resist, the carrier density modulation in the graphene underneath the metal electrodes should be considered when discussing the metal/graphene contact.