▎ 摘　　要

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 2 pi-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 root 3 x 6 root 3)-R30 degrees, from that of the SIC substrate. Clear diffraction rings due to the intra-layer C-C 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. (C) 2014 Elsevier B.V. All rights reserved.