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° off-axis are presented. The STM images show that there is superimposed on $1×1$ graphene pattern the carbon nanomesh of honeycomb $6×6$ structure with the lattice vector of 17.5 Å. The TEM results give evidence that the first carbon layer is separated by 2 Å from the Si-terminated SiC surface and that subsequent carbon layers are spaced by 3.3 Å. It is also found in TEM that the graphene layers cover atomic steps, present on 4° 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.