Local atomic configuration of graphene, buffer layer, and precursor layer on SiC(0001) by photoelectron diffraction

Abstract

The layer-specific atomic structure of the 4H-SiC(0001) surface at each stage of single-layer graphene formation was studied using photoelectron diffraction. The 2π-sr C 1s photoelectron intensity angular distributions (PIADs) excited by circularly-polarized soft X-ray were measured. Taking the photoelectron inelastic mean free path into account, we have separated C 1s PIADs of the graphene overlayer together with the interface buffer layer beneath it and the precursor layer, (6√3×6√3)-R30°, from that of the SiC substrate. Clear diffraction rings due to the intra-layer CC bond scattering of graphene were observed. The forward focusing peaks indicating the directions of the neighboring atoms seen from the C atoms directly bonded to the SiC substrate were observed for the precursor and interface buffer layers. This result suggests that the structures of both layers have a common local atomic configuration.