Understanding the origin of band gap formation in graphene on metals: graphene on Cu/Ir(111)

TL;DR

This study investigates how intercalating a Cu monolayer between graphene and Ir(111) modifies the electronic structure, especially the band gap formation at the Dirac point, using combined experimental and theoretical methods.

Contribution

It introduces a methodology to analyze band hybridization mechanisms at graphene/metal interfaces and predicts electronic structures of similar systems.

Findings

Intercalation modifies the graphene band structure and charge distribution.

Band hybridization contributes to the opening of the band gap at the Dirac point.

The methodology can predict electronic structures of other graphene-metal interfaces.

Abstract

Understanding the nature of the interaction at the graphene/metal interfaces is the basis for graphene-based electron- and spin-transport devices. Here we investigate the hybridization between graphene- and metal-derived electronic states by studying the changes induced through intercalation of a pseudomorphic monolayer of Cu in between graphene and Ir(111), using scanning tunnelling microscopy and photoelectron spectroscopy in combination with density functional theory calculations. We observe the modifications in the band structure by the intercalation process and its concomitant changes in the charge distribution at the interface. Through a state-selective analysis of band hybridization, we are able to determine their contributions to the valence band of graphene giving rise to the gap opening. Our methodology reveals the mechanisms that are responsible for the modification of the electronic structure of graphene at the Dirac point, and permits to predict the electronic structure of other graphene-metal interfaces.