| Carbon nanotubes (CNTs) are promising materials for future nanoelectronic applications thanks to their excellent electrical and thermal transport properties and the quasi one-dimensional nanostructure. However, there are many structural forms of CNTs and each has its own properties. Correlation of structure and electrical transport properties is still ambiguous. In this thesis, a novel design of field-effect transistor is proposed and constructed. This unique device architecture allows us not only to investigate the electrical transport properties of the nanotubes, but also to characterize atomic structures of the same nanotubes by transmission electron microscopy (TEM). The results obtained form the combined electrical transport measurements and structural characterizations are presented. The current-voltage (I-V) characteristics are interpreted in terms of structural forms of nanotubes. Examples include single-walled nanotube with an intramolecular junction, double-walled nanotube, and nanotube bundles. Depending on the tube configuration with respect to the external electric field, the I-V characteristics are dramatically changed. Comparison with ab initio simulations done at North Carolina State University show that the screening of the electric field breaks the cylindrical symmetry of the tubes and affects their band structure, which is supported by experiments. These results emphasize the importance of atomic structure characterization to our understanding of the electrical transport properties of nanotubes and provide a general approach for future studies of structure-property relationships in 1D nanostructures. |
