The relationship between the band-gap and the vacancy density was investigated from first principles. The range influence of a vacancy defect due to structural deformation was characterized and a microscopic explanation was proposed to relate the structural deformation to the band-gap variation. In order to investigate the effect of the defect density on C nanotube, 5 models of (5,5) armchair C nanotubes were built with the defect density as one vacancy per 79, 119, 159, 199 and 239 carbon atoms, respectively. The long range of influence of a MVD was characterized by structural deformation analysis and the strain caused by the MVD was the main reason to cause the strong fluctuation in band-gap of the defected armchair single-walled C nanotubes. However, no simple correlation between the MVD density and band-gap were found. The results shed some light on the instability of the defected armchair single-walled C nanotubes in electronic properties synthesized via ion-irradiation.

Influence of Vacancy Defect Density on Electrical Properties of Armchair Single Wall Carbon Nanotube. L.G.Tien, C.H.Tsai, F.Y.Li, M.H.Lee: Diamond and Related Materials, 2008, 17[4-5], 563-6