Interactions Between Epitaxial Graphene Grown on the Si- and C-Faces of 4H-SiC Investigated Using Raman Imaging and Tip-Enhanced Raman Scattering

Interactions between epitaxial graphene grown on Si- and C-faces were investigated using Raman imaging and tip-enhanced Raman scattering (TERS). In the TERS spectrum, which has a spatial resolution exceeding the diffraction limit, a D band was observed not from graphene surface, but from the edges of the epitaxial graphene ribbons without a buffer layer, which interacts with SiC on the Si-face. In contrast, for a graphene micro-island on the C-face, the D band disappeared even on the edges where the C atoms were arranged in armchair configurations. The disappearance of the edge chirality via combination between the C atoms and SiC on the C-face is responsible for this phenomenon. The TERS signals from the C-face were weaker than those from the Si-face without the buffer layer. On the Si-face with a buffer layer, the graphene TERS signal was hardly observed. TERS enhancement was suppressed by interactions on the edges or by the buffer layer between the SiC and graphene on the C- or Si-face, respectively.