Adsorption of fullerene and azafullerene on Cu(111) studied by electron energy loss spectroscopy

Fullerene and azafullerene films were studied by electron energy loss spect roscopy in reflection geometry. Compared to C-60, (C59N)(2) multilayers sho w additional vibrational modes that are characteristic of the dimer structu re. The (C59N)(2) is semiconductor-like and giant optically allowed exciton ic transitions are found in the gap in drastic contrast with C-60. The azaf ullerene monolayer on Cu(111) no longer shows the presence of dimers, indic ating monomer adsorption. Similarly to C-60, azafullerene molecules in cont act with the metal substrate receive a transferred charge between two and t hree electrons. However, the C59N appears more covalently bound to Cu becau se it decomposes when heated above 660 K while C-60 only desorbs. (C) 2001 Elsevier Science B.V. All rights reserved.