Modifications to the Electronic Structure of Carbon Nanotubes with Symmetric and Random Vacancies

摘要

The influence of different types of atomic vacancies on the electronic structure of carbon nanotubes(20,0)and(12,12)was investigated using an empirical tightbinding method.The models with vacancies randomly and symmetrically arranged in an extended unit cell were constructed.The symmetrical distribution of defects was obtained by rotating a pore,obtained by removing a hexagonal ring from a graphitic shell around the tube axis.The random defects were generated by a specially developed algorithm,which eliminates a given number of atoms from the urit cell so that the remaining carbon atoms have no more than one dangling bond.The presence of vacancies in carbon nanotube causes an enhancement of density of occupied states that is near the Fermi level and whose localization increases with the number of two-coordinated atoms at the pore boundaries.It was found that the occurrence of atomic vacancies in the carbon nanotube walls might result in the narrow-gap semiconductors and ferromagnetic materials.