Electron-energy-loss spectroscopy of C-60 monolayer films on active and inactive surfaces

The characteristics of interaction between C-60 molecules and Si(111)-7 x 7 , Ag/Si(111)-root3 x root3 R30 degrees and layered material MoS2 surfaces h ave been investigated using electron-energy-loss spectroscopy (EELS), The E EL spectrum of C-60/Si(111)-7 x 7 shows a new peak at loss energy of 2.7 eV . This indicates the existence of charge transfer from the substrate to C-6 0 molecules. The EEL spectrum of a C-60 monolayer film grown on a cleaved s urface of MoS2 is almost the same as that of bulk C-60 The EEL spectrum of a C-60 monolayer film on an Ag/Si(111) surface is quite different from that on a clean Si(111)-7 x 7 surface, although the films on those substrates h ave the same epitaxial arrangement. Furthermore, intensities of energy-loss peaks of C-60/Ag/Si(111) are slightly smaller than those of C-60/MoS2 in s pite of having the same loss-energy. This suggests that the interaction bet ween C-60 molecules and the Ag/Si(111) surface is stronger than that betwee n C-60 molecules and the MoS2 surface. (C) 2001 Elsevier Science B.V. All r ights reserved.