Semi-Empirical Studies on Electronic Properties and Applications of Carbon Nanotubes
Li, Yan
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https://hdl.handle.net/2142/34781
Description
Title
Semi-Empirical Studies on Electronic Properties and Applications of Carbon Nanotubes
Author(s)
Li, Yan
Issue Date
2005-12
Doctoral Committee Chair(s)
Ravaioli, Umberto
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Carbon Nanotubes
Transverse Dielectric Response
Metal-Semiconductor Transition
Armchair Carbon
Finite-Size Effect
Language
en
Abstract
Carbon nanotubes are nanostructures with fascinating electrical, mechanical, thermal and chemical properties, which make them an ideal system to test fundamental theories in low-dimensional structures, and at the same time a promising candidate for applications in the field of fast-developing nanotechnology. In this thesis, we have developed a self-consistent tight-binding model to investigate the electronic properties and applications of carbon nanotubes. First, we study the transverse dielectric response and discuss its dependence on nanotube geometry, field strength and position of the Fermi level. We find significant modification of the band structure at the strong field limit. Band gap opening/closing is predicted for metallic/semiconducting zigzag nanotubes, while armchair nanotubes remain metallic due to the high lattice symmetry. Next, we demonstrate the possibility of metal-semiconductor transitions in metallic nanotubes under angular perturbations. With the aid of group theory techniques, we provide selection rules for subband coupling and estimate the magnitude of band gap opening as well Fermi velocity renormalization near the Fermi level. We also suggest an effective mechanism to enhance the metal-semiconductor transition by combination of different forms of perturbations. Finally, we study the finite-size effect on the structural and electronic properties of carbon nanotubes. By combining with first principle calculations and classical molecular dynamics simulations, our model allows us to study the transport behavior of a water molecule or ion interacting with a short nanotube segment. We demonstrate the importance of the nanotube polarization effect and atomic partial charges in determining the energetics of the system, which may facilitate understanding and controlling the electronic behavior of carbon nanotubes in biological applications.
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