View article

Degassing of bundles of single-walled carbon nanotubes in vacuum at 500 K is found to drive the thermoelectricpower (TEP) strongly negative, indicating that the degassed metallic tubes in a bundle are n type. The magnitude of the negative TEP indicates that important asymmetry in the electronic carbon π bands exists near the Fermi energy. Easily measurable increases in the TEP (∼ 5–10 μ V/K) and resistivity (2%–10%) are observed at 500 K upon exposure to N 2 and He, suggesting that even gas collisions with the nanotube wall can contribute significantly to the transport properties.