Spectral ellipsometry of amorphous hydrogenated carbon grown by magnetron sputtering of graphite

Abstract

Polarization angles for films of amorphous hydrogenated carbon produced by magnetron sputtering of graphite in argon-hydrogen plasma have been measured using spectral ellipsometry (in the range of photon energies 1–5 eV). The dispersion of the imaginary and real parts of the permittivity has been reconstructed. It is shown that the data obtained are consistent with the Kramers-Kronig formalism in the frequency range under study. The sum rule allowed us to conclude that the density of states is nonuniformly distributed over energies and to reveal the characteristic threshold energies in the spectrum of the effective density of states (2 and 3.8 eV). The possibility of describing the energy spectrum of electrons using Gaussian curves is shown. The features of the energy distribution of states are attributed to the contribution of the σ and π states.