Band gap engineering by Bi intercalation of graphene on Ir(111)

TL;DR

This study demonstrates how intercalating bismuth beneath graphene on Ir(111) modifies its structure and electronic properties, notably opening a band gap and inducing doping, with insights from microscopy, calculations, and spectroscopy.

Contribution

It provides new understanding of Bi intercalation effects on graphene's electronic structure and the formation of a band gap through combined experimental and theoretical analysis.

Findings

Bi intercalation induces a 0.42 eV band gap at the Dirac point.

Intercalation causes n-doping of approximately 0.39 eV.

Dislocation networks form along the moiré pattern, influencing electronic properties.

Abstract

We report on the structural and electronic properties of a single bismuth layer intercalated underneath a graphene layer grown on an Ir(111) single crystal. Scanning tunneling microscopy (STM) reveals a hexagonal surface structure and a dislocation network upon Bi intercalation, which we attribute to a $\sqrt{3}\times\sqrt{3}R30{\deg}$ Bi structure on the underlying Ir(111) surface. Ab-initio calculations show that this Bi structure is the most energetically favorable, and also illustrate that STM measurements are most sensitive to C atoms in close proximity to intercalated Bi atoms. Additionally, Bi intercalation induces a band gap ($E_g=0.42\,$eV) at the Dirac point of graphene and an overall n-doping ($\sim 0.39\,$eV), as seen in angular-resolved photoemission spectroscopy. We attribute the emergence of the band gap to the dislocation network which forms favorably along certain parts of the moir\'e structure induced by the graphene/Ir(111) interface.