STM images of a 6H-SiC(000-1) sample after graphitization (same sample as in figure 1). (a) 300 × 300 nm2 STM image of few layers of graphene grown on 6H-SiC (000-1). The brightest areas correspond to multilayers grown on a step edge, the right part corresponds to monolayer graphene. (b) 150 × 150 nm2 zoom of the top right corner of image (a). The dark areas correspond to monolayer graphene grown on (3 × 3) SiC-reconstructed surface. MPs are seen on the monolayer and on the multilayers (the brighter area) indicating that the first graphene layer is disoriented compared to the SiC surface and that the multilayers are "twisted" (turbostratic stacking). (c) 50 × 50 nm2 STM images of a bilayer and a monolayer. The turbostratic stacking of the bilayer is revealed by a long-range MP with a wavelength of 4 nm. On the monolayer, one can only see the (3 × 3) SiC surface reconstruction pattern due to the high tunnel voltage (-2.5 V). It should be stressed that the top graphene plane is continuous between the mono and the bilayer. (d) 300 × 300 nm2 STM image showing the distribution of FLG grown ranging from the bare (3 × 3) SiC surface (0L), monolayers (1L), and bilayers (2L). On the left, a 1-nm high wrinkle can be seen on a bilayer. The bright horizontal line corresponds to a tip change.
Tiberj et al. Nanoscale Research Letters 2011 6:171 doi:10.1186/1556-276X-6-171