Preparation of graphene on different-polarity 6H-SiC substrates and the study of their electronic structures

The epitaxial graphene (EG) layers are grown on Si-terminated 6H-SiC (0001) substrates and C-terminated 6H-SiC (000 1 - ) substrates separately by thermal annealing in an ultrahigh vacuum chamber. Low energy electron diffraction(LEED) and synchrotron radiation photoelectron spectroscopy(SRPES) are used to in-situ study the synthesis process, and the prepared samples are characterized by Raman spectrum, and near edge X-ray absorption fine structure(XANEX). The results show that we have successfully prepared high-quality EG layers on the two polar surfaces of 6H-SiC. The comparisons studies indicate that Si terminated EG is highly oriented while C terminated EG is anisotropic, and that the interface interaction similar to that of C-sp3 bond of diamond exists on the Si terminated EG, the interaction between the epitaxial film and substrate is stronger, while on the C terminated EG there is no such interaction, and the interaction between the epitaxial film and substrate is weaker.