Preparation Of Carbon Nanotubes With Heterogeneity Junctions And Research On The Electric Properties Of Small Energy Gap Single Walled Carbon Nanotubes

Carbon nanotube is one kind of new carbon material. Since its discovery, the carbon nanotube has become the focus of varies researching field. Since the lattice periodicity and its vibration importantly affect the physical properties of a material, such as strength, heat, light, electricity, the research on carbon nanotube's electric properties is extremely important to its nanodevice applications.A new way for Synthesis the single walled carbon nanotubes (SWNT) bundles, ropes, and those with heterogeneity junctions in arc discharge method and their characterizations are discussed within chapter 2.The electric property of carbon nanotube varies with the rolled up chiral indices, so as the dimentionality of it has a profonund influence on its physical behaviors. While the carbon nanotubes are ideal material to test the exotic 1D electronic properties of such materials, which has been a long standing wish of condensed matter physicists. Their exceptional properties can also be exploited in numerous technological applications. Especially, they can also be used as the active elements in nanoelectronic devices . In chapter 3, we derived the 2D graphene as well as the zigzag and armchair SWNTs' energy band structures by using the Hückel Molecular Orbital (HMO) theory.In chapter 4, we will discuss in detail the finite curvature effect and symmetry broken effect on the intrinsic electronic properties of SWNTs. We show that 'metallic' zigzag nanotubes have energy gaps, and armchair nanotubes packed in bundles have pseudo gaps, which exhibit an inverse dependence on tube radius.In chapter 5 , the computation of first principle as well as Non-equilibrium Green Function and Density Functional Theory are used to determine the transmission property of the Single Walled Carbon Nanotubes with 5-7 element loop defects. As a result, the energy band structures of the (7,0)-(8,0) and (8,0)-(9,0) SWNTs' heterojunctions are calculated and compared to those of ideal (7,0), (8,0), (9,0) SWNTs. It shows that different junction mode can evidently affect the transmission property of electrons. This character may be great valuable to molecular electronic devices developing, e.g. the field effect transistors in normal temperature.