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

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