Thermal induced transition in the bonding nature of C60 molecules adsorbed on a Si(111)–(7×7) surface

Autor: Akito Kakizaki, Kazuyuki Sakamoto, Daiyu Kondo, Shozo Suto, Yoshimitsu Ushimi, Akio Kimura, Masashi Harada
Rok vydání: 1999
Předmět:
Zdroj: Journal of Electron Spectroscopy and Related Phenomena. :413-418
ISSN: 0368-2048
Popis: We have investigated the electronic structure and the thermal dependence of C 60 molecules adsorbed on a Si(111)–(7×7) surface using photoelectron spectroscopy. At room temperature, the binding energies of the molecular orbitals and the C 1 s core level of the 1.0 monolayer (ML) film are the same as those of the 5.0 ML C 60 film. This result indicates that most of C 60 molecules interact with the Si surface by van der Waals force at a coverage of 1.0 ML. After annealing the 1.0 ML C 60 film at 500 K, the full-width at half maximum of the molecular orbitals becomes broader indicating the chemisorption at this temperature. Moreover, the highest occupied molecular orbital (HOMO) of a C 60 molecule splits into two peaks that are assigned to be the shifted HOMO and the bonding state with the polarization-dependent measurements and the Si 2 p core level spectrum. The molecular orbitals and the C 1 s core level shift to lower binding energies. These results indicate that the chemisorption between C 60 molecules and the surfaces has both covalent and ionic characters at 500 K. We attribute the transition in the bonding nature of C 60 molecules to the thermal induced change in surface structure during the annealing process.
Databáze: OpenAIRE
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