The electronic structure of the 3 root 3 x 3 root 3R30 degrees-C-60/Ge(111) system as measured by angle-resolved photoemission

We have investigated the close packed 3 root 3 x 3 root 3R30 degrees-C-60 m onolayer on the Ge(111) surface using synchrotron radiation photoemission. No filling of the lowest unoccupied molecular orbital (LUMO) derived bands has been observed. The C 1s core level and the valence band photoemission s pectra point to the presence of a localized covalent bond between the C-60 molecules and the Ge atoms. This bond induces the splitting of the C-60 hig hest occupied molecular orbital (HOMO) with a new feature appearing at abou t 2.3 eV. The Ge 3d core level spectra show the quenching of the surface fe atures related to the adatoms/rest atoms complex, suggesting that the obser ved 3 root 3 x 3 root 3R30 degrees ordering is not due to a Ge(111) reconst ruction induced by the C-60 adsorption. (C) 2000 Elsevier Science B.V. All rights reserved.