title: Dynamical conductivity of boron carbide: heavily damped plasma vibrations.
abstract: The FIR reflectivity spectra of boron carbide, measured down to ω~10 cm(-1) between 100 and 800 K, are essentially determined by heavily damped plasma vibrations. The spectra are fitted applying the classical Drude-Lorentz theory of free carriers. The fitting Parameter Π=ωp/ωτ yields the carrier densities, which are immediately correlated with the concentration of structural defects in the homogeneity range. This correlation is proved for band-type and hopping conductivity. The effective mass of free holes in the valence band is estimated at m*/me~2.5. The mean free path of the free holes has the order of the cell parameters.
authors.affiliation: Institute of Physics, University Duisburg-Essen, Campus Duisburg, D - 47048 Duisburg, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Werheit
authors.forename: Guido
authors.initials: G
authors.lastname: Gerlach