Vibrational Modes of C₆₀ Fullerene on Si(111)7×7 Surface: Estimation of Charge Transfer from Silicon Dangling Bonds to C₆₀ Molecules

Abstract

We have investigated vibrational modes of C 60 monolayer film adsorbed on the Si(111)7×7 surface using high-resolution electron-energy-loss spectroscopy in combination with scanning tunneling microscopy. The differences in energies and in oscillator strengths from a thick C 60 film (i.e., bulk C 60 ) are discussed in terms of the charge transfer from silicon dangling bonds to C 60 molecules. The amount of charge transfer is estimated to be 1±1 electron(s) compared with the infrared absorption spectra of alkaline-doped C 60 fullerides and with the weak electron-molecular-vibration coupling calculation.