Structural and physical properties of torsional carbon nanotube devices by electron diffraction and microscopy

Cui, Taoran

Structural and physical properties of torsional carbon nanotube devices by electron diffraction and microscopy Public Deposited

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March 21, 2019

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Cui, Taoran
- Affiliation: College of Arts and Sciences, Department of Physics and Astronomy

Abstract

This dissertation first probes into the detailed development process of a nanoelectromechanical system based on one-dimensional carbon nanotubes. Various types of carbon nanotubes with a sparse spatial distribution are grown with corresponding chemical vapor deposition recipes. The synthesis is followed by the microelectronic fabrication to pattern a circuit with a suspended carbon nanotube, which allowed the in situ observation and manipulation of this nano-electromechanical system in a transmission electron microscope. The theoretical deduction and the experimental result prove the sophistication of in situ nanobeam electron diffraction with transmission electron microscopy to determine the chiral structure of a carbon nanotube, especially each individual inner shell of a multiwalled carbon nanotube, while the electron transport behavior of the carbon nanotube is measured. Based on the experimental results of large numbers of carbon nanotubes, a model is established to correlate the transport property with the atomic structure of a carbon nanotube. Given the unambiguous chirality and therefore the explicit band structure, it is concluded that both the thermal excitation and the multiple conducting subbands significantly contribute to the ballistic transport in a carbon nanotube at room temperature. External torsional strains are applied on a carbon nanotube via a nano-pendulum system fabricated with the similar techniques. The corresponding deformations are determined with nanobeam electron diffraction analysis, and the calculated shear moduli agree with the theoretical predictions and other experimental results. This nano-pendulum with a multiwalled carbon nanotube provides a perfect platform to study friction. The interlayer interactions and the frictions are investigated by monitoring the relative motions between the neighboring shells when the carbon nanotube undergoing a torsional strain. Furthermore, The resistance variations of a carbon nanotube responding to strains are also measured in situ at room temperature, and the transport behavior of a deformed carbon nanotube is successfully explained by our established model.

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