Effects of topological defects on the electronic structure and optical spectrum of single-wall carbon nanotubes

The energy band structures, optical absorption spectra and reflectivity of the semiconducting single-wall carbon nanotubes (7,0) and (8,0), with symmetrical Stone-Wales defects on (7,0) and symmetrical Stone-Wales defects on (8,0). and (7,0)-(8,0) SWCNT heterojunction were studied using the density functional theory, and the results were compared. It is shown that the energy band structures have changed obviously, and according to different kind of defects the Fermi energy levels were shifted in different direction. The absorption and reflectivity weakened obviously and red shift of absorption peak and reflectivity peak have occurred in the lower energy region, when the carbon nanotube contained topological defects compared to perfect single-wall carbon nanotubes. There was a distinct peak in the five carbon nanotubes at the photon energy of about E= 13 eV, and the peak shifted to high energy region when the nanotube contained defects. The results were analyzed and discussed theoretically. The authors can take advantage of the photoelectricity property created by topological defect to design photoelectricity device.