Bonding nature of C60 adsorbed on Si(111) 7 × 7 and Si(100) 2 × 1 surfaces studied by HREELS and PES

S. Suto, K. Sakamoto, D. Kondo, T. Wakita, A. Kimura, A. Kakizaki

Research output: Contribution to journalConference article

17 Citations (Scopus)

Abstract

We report here the measurements of vibrational excitation spectra, valence band spectra and C 1s core level spectra of C60 molecules adsorbed on Si(111) 7 × 7 and Si(100) 2 × 1 surfaces, using high-resolution electron energy loss spectroscopy (HREELS) and photoelectron spectroscopy (PES). At a coverage between 1 and 0.25 ML, HREELS and PES measurements show that the interaction is as weak as the van der Waals interaction on both surfaces. At a coverage lower than 0.25 ML, some contradictory results are obtained by HREELS and PES. With HREELS, the softening of several vibrational modes is observed on the Si(111) 7 × 7 surface, but no indication of softening is observed on the Si(100) 2 × 1 surface. The charge transfer scheme explains the softening well. These results by HREELS indicate that the nature of the bonding is ionic on the Si(111) 7 × 7 surface and of the van der Waals type on the Si(100) 2 × 1 surface. In contrast, the bonding states between C60 molecules and Si substrates are clearly observed at 2.4 eV on both surfaces with PES. The PES measurements indicate that the interaction has a covalent character on the Si(111) 7 × 7 surface, and that it is in between covalent and ionic, i.e. not purely ionic or at the covalent limit, on the Si(100) 2 × 1 surface. We will discuss the nature of the interaction manifested by HREELS and PES measurements in comparison with the spectra of C60 molecules adsorbed on metal surfaces.

Original languageEnglish
Pages (from-to)85-90
Number of pages6
JournalSurface Science
Volume427-428
DOIs
Publication statusPublished - Jun 1 1999
Externally publishedYes
EventProceedings of the 1998 9th International Conference on Vibrations at Surfaces (VAS9) - Kanagawa-ken, Jpn
Duration: Oct 12 1998Oct 16 1998

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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