OPTICAL-CONSTANTS OF HYDROGENATED AMORPHOUS-CARBON IN THE RANGE 0-100 EV

The dielectric behavior of hydrogenated amorphous carbon samples, prepared by keV-Ar-ion bombardment of a polystyrene matrix, in the energy range 0- 100 eV has been studied in connection with the change in hydrogen content. The wide-ranging results obtained by means of electron-energy-loss spectroscopy in reflection mode have been successfully compared with the optical constants available in the 1-6 eV range, resulting from the combined use of transmittance and reflectance experimental spectra. A strong rearrangement of the sigma --> sigma* transitions is evidenced in the bulk loss function Im( - 1/epsilon) together with a change in the relative oscillator strengths, on going from pure amorphous carbon to the most hydrogenated (x(H) = 40%) alpha-C:H sample.