Electronic Superstructures Observed by Scanning Tunneling Microscopy on Graphene Sheet in Vicinity of Nano-Defects of Ir(111) Substrate

Two-dimensional electronic and atomic superstructures (SS) on monolayer graphite (graphene) grown on a clean Ir(111) surface were observed near substrate nano-defect sites by scanning tunneling microscopy. These SS were found rotated 30° with respect to the undistorted areas (away from defects sites) of the graphene layer with a periodicity of and a(a = 2.46 Å)decay over a distance of few nanometers away from the defects. The observed SS were not due to real surface reconstruction, rather they just had an electronic nature.