Peculiar covalent bonding of C₆₀/6H-SiC(0 0 0 1)-(3 × 3) probed by photoelectron spectroscopy

Abstract

High resolution photoemission with synchrotron radiation was used to study the interface formation of a thin layer of C60 on 6H−SiC(0001)-(3 × 3), characterized by protruding Si-tetramers. The results show that C60 is chemisorbed by orbital hybridization between the highest-occupied molecular orbital (HOMO) and the pz 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 2p spectra reveal that a large fraction (at least 45%) of the Si adatoms remain unbound despite the reactive character of the associated dangling bonds. This is consistent with a model in which each C60 is attached to the substrate through a single covalent C60-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 C60 molecules to the substrate via the formation of donor-like interface states.

Phthalocyanine reactivity and interaction on the 6H-SiC(0001)-(3 × 3) surface investigated by core-level experiments and simulations

“…4. The Si 2p core level spectrum of the clean 6H-SiC(0001)-(3 Â 3) surface, exhibiting the expected shape, 19 is deconvoluted into five components. The bulk component is located at 100.66 eV and three surface states located at 100.13 eV, 99.34 eV and 98.64 eV correspond to the silicon atoms involved in the last Si-C bilayer (S3), silicon atoms composing the Si adlayer and the base of the tetramers (S2) and Si adatoms' apex of the tetramers (S1), respectively.…”

“…16,17 Molecule adsorption on the silicon terminated 6H-SiC(0001)-(3 Â 3) surface has also been previously explored. It has been demonstrated experimentally by scanning tunneling microscopy (STM) and core level photoemission spectroscopy and theoretically that H 2 Pc 18 and C 60 19 organic molecules deposited on 6H-SiC(0001)-(3 Â 3) form a covalent bond with the Si adatom of the SiC surface. Singular insulating contact with the SiC surface has also been evidenced with a perylene molecule derivative.…”