Native graphene oxides at graphene edges

The boundary between graphene flake and SiO 2 /Si substrate have been probed by scanning capacitance microscopy. Distinctive dot-like protrusions standing on the graphene edges have been observed, and the density of protrusions increases with the increase of graphene layer numbers. Spectroscopic analysis has revealed that the carrier densities at these protrusions are lower than those of the graphene. In addition, the size of the protrusions is decreased by annealing under reductive gas atmosphere.