Peculiar covalent bonding of C 60 /6 H -SiC(0 0 0 1)-(3 × 3) probed by photoelectron spectroscopy

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High resolution photoemission with synchrotron radiation was used to study the interface formation of a thin layer of C 60 on 6 H -SiC(0 0 0 1)- , characterized by protruding Si-tetramers. The results show that C 60 is chemisorbed by orbital hybridization between the highest-occupied molecular orbital (HOMO) and the p z orbital of Si adatom at the apex of the tetramers. The covalent nature of the bonding was inferred from core level as well as valence band spectra. The Si 2 p spectra reveal that a large fraction (at least ) of the Si adatoms remain unbound despite the reactive character of the associated dangling bonds. This is consistent with a model in which each C 60 is attached to the substrate through a single covalent C 60 –Si bond. A binding energy shift of the core levels associated with sub-surface Si or C atoms indicates a decrease of the SiC band bending caused by a charge transfer from the C 60 molecules to the substrate via the formation of donor-like interface states.