| Since their discovery in 1991, carbon nanotubes (CNs) have drawn a great deal of attention because of their significance in both fundamental science and potential applications. Carbon nanotubes can be now produced by many conventional methods, but the products have disordered and unsorted structures and are oriented randomly. It is desirable and still a challenge to produce aligned and mono-sized single wall carbon nanotubes (SWCNs) with well defined symmetry. This thesis will report a unique method to produce mono-dispersed carbon nanotubes. The task of this thesis is to characterize the structure of carbon nanotubes formed in the channels of AFI and investigate on their physical properties.; The carbon nanotubes are formed by pyrolysis of organic materials tripropylamine (TPA) in the one-dimensional channels of zeolite AlPO4-5 (AFI) crystals. The nanotube structure is confirmed by various techniques including Polarized optical microscopy, transmission electron microscopy (TEM), scanning tunneling microscopy (STM) etc. Single crystal X-ray diffraction shows that the diameter of the nanotubes is about 5 Å. The fabrication of monodispersed SWCNs in three-dimensional ordered and nano-sized channels represents an important step toward the development and applications of carbon nanotube materials.; The vibrating properties of the CNs have been studied systematically by micro-Raman spectra. The symmetries of radial breathing mode and three tangential vibrating modes are identified for the first time. The frequencies of these modes are a little higher than what expected for a free-standing CN, due to the repulsive interaction between carbon nanotubes and the zeolite framework.; The electronic properties have been investigated by electrical transport measurement at temperature from 300 to 0.3 K and in the transverse magnetic field from 0 to 14 T. Near the zero-voltage, the conduction can be attributed to one-dimensional variable-range hopping. In weak electrical field, the field induces enhancement of conductivity, which is responsible to the non-linearity of I-V curves. In strong electrical field and at low temperature, the I-V curves are consistent with Poole-Frenkel effect. In transverse magnetic field, the nanotube samples demonstrate negative magneto-conductance, which can be well explained by spin-dependent variable-range-hopping mechanism. In conclusion, the nanotube sample behaves as a one-dimensional metal with strong localization. |
