ELLIPSOMETRIC DETERMINATION OF THE OPTICAL-CONSTANTS OF C60 (BUCKMINSTERFULLERENE) FILMS

We report the first ellipsometric measurement of the fundamental optical constants (n,k) of C60 films deposited on Si(100) and Au overcoated Si(100) substrates. We obtain a highest occupied molecular orbital-lowest unoccupied molecular orbit (HOMO-LUMO) gap value of 2.3 eV, slightly larger than the gap values obtained from the x-ray photoelectron spectroscopy and electron-energy-loss spectroscopy experiments. The structure observed in the UV is discussed in terms of single-electron excitations across the HOMO-LUMO gap.