VIBRATIONAL PROPERTIES AND STRUCTURE OF C-60 THIN-FILMS ON SI(111)-(7X7) AND GRAPHITE SURFACES

We have investigated the vibrational modes of C-60 thin films adsorbed on the Si(111)-(7 x 7) and graphite surfaces using high-resolution el ectron energy-loss spectroscopy in combination with scanning tunneling microscopy (STM). The energy-loss spectra are different in energies a nd in oscillator strengths for the two surfaces. The differences are a ttributed to the surface morphology observed with STM. The relation be tween macroscopic dielectric theory manifested by electron energy loss and microscopic structure measured with STM is discussed in terms of dielectric function theory.