Large Bandgap Opening Between Graphene Dirac Cones Induced by Na Adsorption onto an Ir Superlattice

TL;DR

This study demonstrates that Na adsorption on graphene on Ir(111) induces a significant bandgap of 740 meV while maintaining high charge carrier velocity, revealing potential for electronic applications.

Contribution

It shows that Na adsorption can open a large bandgap in graphene on an Ir superlattice, a novel approach for bandgap engineering.

Findings

Na adsorption causes a 1.4 eV shift in Fermi level.

Na adsorption opens a 740 meV bandgap in graphene.

High group velocity of charge carriers is preserved.

Abstract

We investigate the effects of Na adsorption on the electronic structure of bare and Ir cluster superlattice covered epitaxial graphene on Ir(111) using angle-resolved photoemission spectroscopy and scanning tunneling microscopy. At Na saturation coverage a massive charge migration from sodium atoms to graphene raises the graphene Fermi level by about 1.4 eV relative to its neutrality point. We find that Na is adsorbed on top of the graphene layer and when coadsorbed onto an Ir cluster superlattice it results in the opening of a large bandgap of {\Delta} = 740 meV comparable to the one of Ge and with preserved high group velocity of the charge carriers.