Helium Atom Scattering from Graphene Grown on Rh(111)

Abstract

Graphene growth on transition-metal surfaces leads to an ordered superlattice that appears as a series of hills and valleys in scanning tunneling microscopy. On Rh(111), the graphene forms an incommensurate epitaxial overlayer; the crystallographic axes of the graphene are closely aligned with the Rh(111) surface lattice vectors, but the Rh and graphene lattice constants are significantly different. Thus, the C atoms sit over different positions of the Rh(111) lattice and their height above the Rh(111) surface varies, but the different binding sites also affect the local electronic structure. Scanning tunneling microscopy is affected by both of these factors. He scattering is more a measure of the geometrical corrugation, the variation of the height of the graphene sheet relative to the Rh(111) surface. We compare the results of He diffraction measurements with those of previous scanning tunneling microscopy measurements to assess the relative geometric and electronic corrugations.