Topographic and electronic contrast of the graphene moire on Ir(111) probed by scanning tunneling microscopy and noncontact atomic force microscopy

摘要

Epitaxial graphene grown on transition-metal surfaces typically exhibits a moire pattern due to the lattice mismatch between graphene and the underlying metal surface. We use both scanning tunneling microscopy (STM) and atomic force microscopy (AFM) to probe the electronic and topographic contrast of the graphene moire on the Ir(111) surface. STM topography is influenced by the local density of states close to the Fermi energy and the local tunneling barrier height. Based on our AFM experiments, we observe a moire corrugation of 35 ± 10 pm, where the graphene-Ir(111) distance is the smallest in the areas where the graphene honeycomb is atop the underlying indium atoms and larger on the fcc or hcp threefold hollow sites.