Local-field effects on photoemission ofC60

Abstract

The surface core-level shift in C 1s soft x-ray photoemission spectroscopy has been experimentally observed in films of C 60 on Al. A value of 0.100Ϯ0.025 eV has been determined. Theoretical calculations are presented which show that the core hole is uniformly screened by the C 60 molecule, and that the effect of the surface upon this intramolecular screening should be negligible. The observed SCLS can therefore be accounted for by the difference in final state ͑core hole ϩ polarized near-neighbor molecules͒ between bulk and near-surface atoms, as calculated by a straightforward, real-space, local-field calculation.

Electronic surface reconstruction and correlation in the fcc and dimer phases ofRbC60

“…36, studies of chemisorbed C 60 suggest that intramolecular Madelung potential-like effects are quite small for C 60 , presumably due to the excellent internal polarization of the molecule upon charging. 37 Therefore, we attribute the observation of distinct components in the C 1s spectrum to the existence of different molecular sites rather than to different atomic sites on the same molecule. In the following, we shall accordingly speak of distinct C 60 components when referring to the C 1s and valence-band spectra.…”

Time-resolved photoelectron spectroscopy of low-energy excitations of 4×4 C60/Cu(111)

“…Zhu and coworkers [74] showed that going from 20 to 2 ML fullerite on Cu(111) U decreases to 0.3 eV, which is in agreement with figure 2.7. In the surface layer U is 1.0 eV [40,100]. For a free C 60 the Hubbard energy is U = 3.0 eV [31].…”

“…Further MLs show the spectrum of fullerite. In 2004 Louie and coworkers [72] calculated by means of DFT the electron redistribution for the adsorption of a single C 60 molecule on Au(111) and on Ag (100). Similarly Wang and Cheng [73] calculated the electron redistribution for the adsorption of one ML on Cu (111).…”

On interface dipole layers between C 60 and Ag or Au

“…The energy difference between E A and E I (the conductivity gap) is reduced by a factor of 2 when comparing the energy levels of an isolated molecule with those of a C 60 monolayer on Ag (111). Values taken from [13,21,[34][35][36][37][38][39] In the system depicted by Fig. 1c, the metal stabilizes the charged state of the C 60 -ion, since the metal effectively screens the ion.…”