It was shown that the presence of a local topological defect (pentagon-heptagon pair) in the structure of carbon nanotubes led to the formation of a heterojunction. Tight-binding calculations of the π-electron density of states of the bend junction were carried out.

Electronic Properties of Carbon Nanotubes with Defects. Y.I.Prylutskyy, O.V.Ogloblya, P.C.Eklund, P.Scharff: Synthetic Metals, 2001, 121[1-3], 1209-10