ON THE TEMPERATURE-DEPENDENCE OF ELECTRICAL-CONDUCTIVITY OF BUCKYTUBE-CONTAINING CARBONACEOUS SAMPLES

We have examined the electrical conductivity, sigma(T), from 4.2 to 295 K of samples from a series of buckytube-containing carbonaceous deposits prepared under helium pressures ranging from 20 to 750 Torr. The results show that while absolute values of conductivity are very sample dependent, all temperature variations can be expressed as sigma(T) = C exp(AT) where C and A are positive coefficients. We discuss the results in the light of thermally activated tunnelling based on a two level model.