| Carbon nanotubes are one-dimensional materials that show great promise for next generation electronic devices. To realize the full potential of carbon nanotubes, it is important to understand their intrinsic electronic properties, as well as their interactions with external species. This work has been focusing on the following aspects: (1) We studied the work functions of single wall carbon nanotubes with an experimentally-relevant diameter range and found that the work function can strongly depend on the tube diameter. We showed that both surface dipole and bulk electronic structure contribute to the observed work function change in small diameter tubes. Tubes larger than 1 nm show negligible work function dependence on diameter. (2) We extended the work function study to double wall nanotubes, where the work function value can be predicted using the charge equilibration model. We also observed considerable charge transfer and self-doping of the outer shell when the confined inner shell is a small-diameter zigzag tube. (3) We studied the mechanism of field emission from nanotube tips stimulated by an external beam. Based on our molecular orbital calculation, we propose that beam-stimulated field emission is due to the electrostatic potential change induced by the electrons from the primary beam. (4) We studied in detail the band gap change induced by cross-sectional deformation in single wall nanotubes. It was found that semiconducting and metallic tubes respond quite differently to similar mechanical deformation. Based on the simulation results, we have designed a nanoscale quantum dot device using a doubly bent nanotube, which is predicted to show single electron effects at room temperature. (5) We studied the Schottky barrier formation at the metal/nanotube junction, taking into account the detailed atomistic geometries. It was found that two most important factors that influence the Schottky barrier height are the metal species and surface orientation. We also observed the existence of a tunneling barrier at the gold/nanotube interface. |
