DIELECTRIC AND OPTICAL-PROPERTIES OF C-60 MATERIAL STUDIED BY ELLIPSOMETRY AND QUANTITATIVE IR AND UV VIS SPECTROSCOPY/

Optical properties in the spectral range from 0.06 to 5.5 eV of fuller ite films on different substrates, C-60 powder, and dissolved fulleren e material are investigated by spectroscopic ellipsometry and optical transmission and reflection measurements. Depolarization effects are t aken into account during determination of the dielectric function of f ullerite films by ellipsometry. The optical gap for C-60 films is foun d to be 1.63 eV. Three optical absorption bands are observed at 2.69, 3.53, and 4.49 eV. The dielectric function in the infrared shows the f our characteristic infrared vibrational modes. The interference patter n seen in UV/VIS reflection measurements are used for high-precision t hickness determination of the films. The Clausius-Mossotti formula is successfully applied to reproduce the experimental optical data measur ed in C-60/dichlormethane solutions. Deviations between theory and exp eriments provide interesting information about the intermolecular inte raction of the C-60 molecules. A tentative interpretation of the measu red absorption bands is presented.