Contact resistance in graphene-based devices

TL;DR

This study systematically investigates contact resistance at Ti-graphene interfaces, revealing it is consistent across different graphene layer counts and unaffected by gate voltage or temperature, due to charge transfer effects.

Contribution

It provides the first comprehensive comparison of contact resistance across single, bi-, and tri-layer graphene, highlighting charge transfer as the key factor.

Findings

Contact resistance is approximately 800 Ω·μm for all graphene layers.

Contact resistance is independent of gate voltage and temperature.

Charge transfer causes Fermi level shifts under contacts.

Abstract

We report a systematic study of the contact resistance present at the interface between a metal (Ti) and graphene layers of different, known thickness. By comparing devices fabricated on 11 graphene flakes we demonstrate that the contact resistance is quantitatively the same for single-, bi-, and tri-layer graphene ($\sim800 \pm 200 \Omega \mu m$), and is in all cases independent of gate voltage and temperature. We argue that the observed behavior is due to charge transfer from the metal, causing the Fermi level in the graphene region under the contacts to shift far away from the charge neutrality point.