Structural Coherency of Graphene on Ir(111)

Low-pressure chemical vapor deposition allows one to grow high structural quality monolayer graphene on Ir(111). Using scanning tunneling microscopy, we show that graphene prepared this way exhibits remarkably large-scale continuity of its carbon rows over terraces and step edges. The graphene layer contains only a very low density of defects. These are zero-dimensional defects, edge dislocation cores consisting of heptagon-pentagon pairs of carbon atom rings, which we relate to small-angle in-plane tilt boundaries in the graphene. We quantitatively examined the bending of graphene across Ir step edges. The corresponding radius of curvature compares to typical radii of thin single-wall carbon nanotubes.