Electronic Properties of Clean Au-Graphene Contacts

TL;DR

This study investigates how gold grains affect the electrical conduction and doping of graphene, revealing p-doping effects, tunneling behavior, and agreement with theoretical predictions for Fermi level shifts.

Contribution

It provides a detailed experimental analysis of Au-graphene contacts, highlighting the tunneling nature and doping effects of gold grains on graphene conduction.

Findings

Au grains cause p-doping in graphene.

The contact exhibits tunneling behavior with giant-phonon thresholds.

Fermi level shift aligns with first principles calculations.

Abstract

The effects of Au grains on graphene conduction and doping are investigated in this report. To obtain a clean Au-graphene contact, Au grains are deposited over graphene at elevated temperature and in high vacuum, before any chemical processing. The bulk and the effective contact resistance versus gate voltage demonstrate that Au grains cause p-doping in graphene. The Fermi level shift is in agreement with first principles calculations, but the equilibrium separation we find between the graphene and the top-most Au layer is larger than predicted. Nonequilibrium electron transport displays giant-phonon thresholds observed in graphene tunnel junctions, demonstrating the tunneling nature of the contact, even though there are no dielectrics involved.