Effects of various defects on the electronic properties of single-walled carbon nanotubes: A first principle study

The geometries, formation energies and electronic band structures of (8, 0) and (14, 0) singlewalled carbon nanotubes (SWCNTs) with various defects, including vacancy, Stone-Wales defect, and octagon-pentagon pair defect, have been investigated within the framework of the density-functional theory (DFT), and the influence of the concentration within the same style of defect on the physical and chemical properties of SWCNTs is also studied. The results suggest that the existence of vacancy and octagon-pentagon pair defect both reduce the band gap, whereas the SW-defect induces a band gap opening in CNTs. More interestingly, the band gaps of (8, 0) and (14, 0) SWCNTs configurations with two octagon-pentagon pair defect presents 0.517 eV and 0.163 eV, which are a little smaller than the perfect CNTs. Furthermore, with the concentration of defects increasing, there is a decreasing of band gap making the two types of SWCNTs change from a semiconductor to a metallic conductor.