Atomic Structures and Electronic Scattering of Graphene Edges

The success of growing monolayer gaphene on Cu foils has stimulated intense interests to study its structural and electronic properties at the atomic scale. Here we present a scanning tunneling microscopy (STM) investigation on single crystalline graphene islands synthesized on polycrystalline Cu foils by chemical vapor deposition (CVD). Our studies reveal that most of the graphene edges are macroscopically parallel to the zigzag directions with microscopic roughness. The observed rough edges follow the zigzag directions at atomic scale and make many 120-degree turns. Strong electron scattering was observed from a rarely-occurring armchair-oriented edge, and there is little such scattering observed from zigzag-oriented edges. In addition, we also observed nearly periodic parallel lines attributed to the surface dislocations of the Cu underneath graphene.