I. Marenne

Reversible Phase Transformation and Doubly Charged Anions at the Surface of Simple Cubic RbC(60)

The simple cubic phase of a RbC60 thin film has been studied using photoelectron spectroscopy. The simple cubic-to-dimer transition is found to be reversible at the film surface. A sharp Fermi edge is observed and a lower limit of 0.5 eV is found for the surface Hubbard U, pointing to a strongly correlated metallic character of thin-film simple cubic RbC60. A molecular charge state is identified in the valence band and core-level photoemission spectra which arises from C60(2-) anions and contributes to the spectral intensity at the Fermi level.

Insulating surface layer on single crystal K3C60

Abstract.Using angle-dependent photoemission spectra of core and valence levels we show that metallic, single crystal K3C60 is terminated by an insulating or weakly-conducting surface layer. We attribute this to the effects of strong intermolecular correlations combined with the average surface charge state. Several controversies on the electronic structure are thereby resolved.

Investigations of thick films of C59N doped with potassium

We investigated (C59N)2 multilayer films, intercalated with different amounts of potassium, by electron energy loss spectroscopy and by synchrotron radiation techniques. For low K exposures, valence band photoemission shows, apart from a rigid shift towards higher binding energies of the whole spectrum, two new LUMO-derived peaks, indicative of a mixture of phases. One of the doped phases still preserves the dimer structure. At K concentrations, the (C59N)2 dimer breaks up, as seen by HREELS, but the dimer phase can be recovered by distillation. C1s and K2p photoemission spectra show two K sites up to about K3C59N and one K site for higher K concentrations.