Effects Of Magnetic Field And Defects On Electronic Structure And Properties Of Carbon Nanotubes

Carbon nanotubes, especially single-walled carbon nanotubes, is an important quasi-one-dimensional nanostructures functional materials,it is also one of the hot spots and the forefront of high-tech research currently. By reason of the special structure of carbon nanotubes, carbon nanotubes have series of new physical effects, small size effect, interface effect, quantum effects and quantum tunnel effect etc. Carbon nanotubes, with a number of unique properties different from traditional materials', is one of the preferred material preparing of nano-electronic devices currently, is also the forefront of the issue on material physics, condensed matter physics and other fields.The band structure and the density of state changes of carbon nanotubes under the magnetic field and the effects of defects symmetry on the electrical properties of carbon nanotubes was studied in this paper.First, the effects of the external magnetic field on the energy gap of carbon nanotubes were investigated by using the tight-bonding method. It was found that , under the axes magnetic field , the peak of energy gap induced by magnetic field depend on the diameters tightly. For the same diameters tubes, the metal type tubes have the highest energy gap peak. Furthermore, under the magnetic field, the density of states of carbon nanotubes near the Fermi level are also calculated, showing that the Van Hove singularities will exhibit a periodic phenomenon of splitting, moving and merging. Hence our research work has practical significance. It will be of great help in-depth study on the magnetic resistance coefficient and orbital magnetic moment such as magnetic properties Carbon nanotubes.In addition, the effects of the Stone-Wales defects symmetry in the carbon nanotubes were researched by using electronic tight-binding model under real space and space Green's function method. The existence of defects will destroy partly or the whole inherent mirror axis of symmetry of the carbon nanotubes, and lead to the changes of the local density of states and the conductance. It can be better understood the conductance and the density of states of carbon nanotubes depend on the symmetry and the intensity of the defects tightly, by analysing the impact of the quasi-bound states from the symmetry of the defects for the conductive channels inherently. To clarify and study on the effects of the symmetry of the defects has a better understanding of the transport properties of carbon nanotubes. It is also very useful to study the related physical properties of carbon nanotubes with defects.