A first-principles calculation study was made of the modification of the electronic structure of a C nanotube which was induced by vacancy-related defects. Three defect configurations which were likely to occur in semiconducting C nanotubes were considered. A vacancy-adatom complex was found to bring about a pair of localized states deep inside the energy gap. A pentagon-octagon-pentagon topological defect produced by the divacancy was structurally stable and gave rise to an unoccupied localized state in the gap. The nature of the partially occupied localized state produced by a substitutional impurity plus a monovacancy was also considered.

Deep Levels in the Band Gap of the Carbon Nanotube with Vacancy-Related Defects. G.Kim, B.W.Jeong, J.Ihm: Applied Physics Letters , 2006, 88[19], 193107 (3pp)