C-Axis Conduction in Low Stage Graphite Intercalation Compounds with Iodine Monochrolide

The intrinsic electrical resistivities in c -direction (ρ c ) of stages-1 and -2 graphite intercalation compounds (GIC) with ICI have been successfully determined. The temperature dependence is qualitatively metallic-like, and does not show any thermal hysteresis so far considered to be characteristic of acceptor-type GICs. Dominant carriers are positive holes not less than 5×10 20 cm -3 . The mobility values whereby computed are too low to deal with the matter on the basis of the band model. An interpretation has been given by Sugihara's “impurity-assisted hopping mechanism” which however is modified so as to take into account the change of the transfer integral J s ( k - k ') caused by thermal change of the interlayer spacing.