Electrical transport in semiconducting carbon nanotubes

Electrical transport measurements have been carried out for a rope of semiconducting single-wall carbon nantoubes in a temperature range from 2.6 to 200 K. At room temperature, the source drain current decreased as the gate voltage was increased, a p-type carrier behavior. However, as the temperature was decreased in a liquid helium temperature, an irregular Coulomb blockade diamonds have been observed. The temperature dependence of the current at large bias voltage in which Coulomb blockade effect is not important has shown an activated behavior, suggesting the tunnel barrier at the tube–metal junctions.