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Effect of c-axis dispersion on the optical properties of acceptor-type graphite intercalation compounds
Phys. Rev. B 31, 3973 – Published 15 March, 1985
DOI: https://doi.org/10.1103/PhysRevB.31.3973
Abstract
The c-face optical reflectance spectra of stage-1 graphite- and graphite-ICl and stage-2 graphite- have been measured in the photon energy range 0.08 to 10 eV. From a Kramers-Kronig analysis of the spectra, the interband contribution to the imaginary part of the dielectric function (ω) has been determined. It is found that a two-dimensional (2D) band-structure model, while describing qualitatively the spectral features below ∼3 eV, requires the use of an effective temperature much greater than the experimental temperature to explain the width of the onset for valence- to conduction-band absorption in the (stage-1 and -2) compounds. The width of a spectral feature associated with valence- to valence-band absorption in the stage-2 compounds is also not explained satisfactorily by the 2D model. It is shown that weak c-axis dispersion provides a natural explanation for the widths of both of these features.
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