Optical reflectance study of the electronic structure of acceptor-type graphite intercalation compounds

Abstract

We have measured the absolute reflectance at near-normal incidence of stage-1--4 graphite-${\mathrm{SbCl}}_{5}$ intercalation compounds in the photon-energy range 0.08--10 eV and have subsequently performed a Kramers-Kronig phase-shift analysis of the data. A separation of free- and bound-charge contributions to the optical dielectric function \ensuremath{\epsilon}(0,\ensuremath{\omega}) is carried out to extract values for the free-carrier (Drude) parameters, charge transfer between intercalate and carbon layers, Fermi-level positions, and important interband transition energies associated with both valence-band--to--valence-band and valence-band--to--conduction-band absorption in the perturbed carbon \ensuremath{\pi} bands. The optical results are compared to previously published two-dimensional energy-band calculations.