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 conducting polymers, in particular the change in sign of the resistivity temperature dependence from metallic to nonmetallic as the temperature is lowered. In analogy to the conducting polymers, we show that a good description of this resistivity behavior is given by a simple model of metallic conduction in aligned nanotubes with hopping or tunneling through small electrical barriers, e.g., tangled regions, inter-rope or intertube contacts, or tubule defects. The model predicts that thermoelectric power in the nanotubes is likely to show metallic behavior down to lower temperatures than resistivity.