Scanning tunnelling microscopic images of metallic and semiconducting single-wall C nanotubes with atomic vacancies were calculated. The tight-binding Green’s function technique and the recursion method were used in the simulations. It was predicted that vacancies should result in the formation of hillock-like features in scanning tunnelling microscopic images of metallic nanotubes, and were especially appreciable at bias voltages of about 0.1 to 0.4V. An enhancement of the tunneling current was attributed to vacancy-induced states at the Fermi energy, and these states were spatially localized on the atoms surrounding the vacancies. Electronic superstructures analogous to those in graphite near to point defects were observed near to the vacancy. For semiconducting nanotubes, hillocks and superstructures were also visible at those bias voltages where band edges contributed to the tunneling current.

Predicted Scanning Tunneling Microscopy Images of Carbon Nanotubes with Atomic Vacancies. A.V.Krasheninnikov: Solid State Communications, 2001, 118[7], 361-5