Graphene on mica probed by scanning tunneling microscopy: networks of ABA and ABC stacked graphene and corrugation of the monolayer
Graphene flakes are prepared on freshly cleaved mica by exfoliation in different environments and studied by scanning tunneling microscopy in ultra high vacuum down to the atomic length scale. On the monolayer, we observed an overall roughness of about 60 pm, after heating the sample to 180{\deg}C which is larger than on similarly prepared multilayers (24 pm) and larger than on monolayers which have been mapped recently by atomic force microscopy without heating (24 pm). A slight preference for a distinct wave length ({\lambda}\simeq8 nm) of corrugations could be determined using an autocorrelation analysis. On few-layer graphene, a triangular network of partial dislocations separating ABC stacked and ABA stacked graphene was found similar to the networks occasionally visible on freshly cleaved HOPG. We found differences in the electronic structure of ABC and ABA stacked areas by scanning tunneling spectroscopy, i.e., a pronounced peak at 0.25 eV above the Fermi level exclusively in the ABA areas, which is largely responsible for the different apparent heights.