Transmission electron microscopy and scanning tunneling microscopy investigations of graphene on 4H-SiC(0001)

Transmission electron microscopy (TEM), scanning tunneling microscopy (STM), and micro-Raman investigations of epitaxial graphene on 4H-SiC on-axis and 4 degrees off-axis are presented. The STM images show that there is superimposed on 1x1 graphene pattern the carbon nanomesh of honeycomb 6x6 structure with the lattice vector of 17.5 A. The TEM results give evidence that the first carbon layer is separated by 2 A from the Si-terminated SiC surface and that subsequent carbon layers are spaced by 3.3 A. It is also found in TEM that the graphene layers cover atomic steps, present on 4 degrees off-axis SiC(0001) surface, indicating a carpetlike growth mode. However, a bending of graphene planes on atomic steps of SiC apparently leads to generation of stress which leads to creation of edge dislocations in the graphene layers.