HETEROGENEOUS MODEL FOR CONDUCTION IN CARBON NANOTUBES

We point out a remarkable similarity between the resistivity behavior observed recently in single-wall carbon nanotubes and that of highly c onducting polymers, in particular the change in sign of the resistivit y temperature dependence Prom metallic to nonmetallic as the temperatu re is lowered. In analogy to the conducting polymers, we show that a g ood description or this resistivity behavior is given by a simple mode l of metallic conduction in aligned nanotubes with hopping or tunnelin g through small electrical barriers, e.g., tangled regions, inter-rope or intertube contacts, or tubule defects. The model predicts that the rmoelectric power in the nanotubes is likely to show metallic behavior down to lower temperatures than resistivity.