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

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 $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}\phantom{\rule{4pt}{0ex}}R{30}^{\ensuremath{\circ}}$ Bi structure on the underlying Ir(111) surface. Ab initio calculations show that this Bi structure is the most energetically favorable and illustrate that STM measurements are most sensitive to C atoms in close proximity to intercalated Bi atoms. Additionally, Bi intercalation induces a band gap (${E}_{\mathrm{g}}=0.42$ eV) at the Dirac point of graphene and an overall $n$ doping $(\ensuremath{\sim}0.39\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$ 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.