Work function at the tips of multiwalled carbon nanotubes

The work function at the tips of individual multiwalled carbon nanotubes has been measured by an in situ transmission electron microscopy technique. The tip work function shows no significant dependence on the diameter of the nanotubes in the range of 14–55 nm. Majority of the nanotubes have a work function of 4.6–4.8 eV at the tips, which is 0.2–0.4 eV lower than that of carbon. A small fraction of the nanotubes have a work function of ∼5.6 eV, about 0.6 eV higher than that of carbon. This discrepancy is suggested due to the metallic and semiconductive characteristics of the nanotube.