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ANALYSIS OF CARBON NANOTUBES
USING NANOELECTROMECHANICAL OSCILLATORS
by
Mehmet Aykol
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(ELECTRICAL ENGINEERING)
August 2012
Copyright 2012 Mehmet Aykol
Object Description
| Title | Analysis of carbon nanotubes using nanoelectromechanical oscillators |
| Author | Aykol, Mehmet |
| Author email | memoman.inc@gmail.com;memoman.inc@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Electrical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2012-06-12 |
| Date submitted | 2012-07-31 |
| Date approved | 2012-07-31 |
| Restricted until | 2012-07-31 |
| Date published | 2012-07-31 |
| Advisor (committee chair) | Cronin, Stephen B. |
| Advisor (committee member) |
Wu, Wei Feinberg, Jack |
| Abstract | In this thesis the thermo-mechanical properties of single–walled carbon nanotubes are investigated utilizing carbon nanotube based nanoelectromechanical oscillators. These resonator devices are highly sensitive to changes in tension on the carbon nanotube. In Chapters 4 the coefficient of thermal expansion of an individual single–walled carbon nanotube is measured in the range 4K - 475K. Experimental observation of this parameter has not been reported before this work and the calculations give different results depending on the models used. The observed negative thermal expansion is attributed to the free configurational space around the carbon atoms of the nanotube. When the nanotube is cooled, the entropy of the system is lowered by expanding the volume of the nanotube through various changes in the structure like pinching twisting or bending. The minimum of the coefficient of thermal expansion is measured as -4.5 ppm•K-1 at 100K. The coefficient of thermal expansion remains negative throughout the entire range. ❧ The mechanical response of carbon nanotube electromechanical oscillators at elevated temperatures is studied in Chapter 5. The weak interaction forces between the carbon nanotube and underlying platinum electrodes limit the performance of carbon nanotube electromechanical oscillators, where the devices are built as described in Chapter 3. Van der Waals bond between the carbon nanotube and the platinum electrode weaken as the temperature increases. At a critical temperature the nanotube delaminates from the surface completely and a sudden drop is observed in the mechanical resonance frequency of the oscillator. Using the results obtained, the clamping force between the carbon nanotube and the underlying platinum electrode is measured to be around 3 pN. The small value obtained for the clamping force shows that quality factor of carbon nanotube electromechanical resonators is affected by the clamping efficiency of the nanotube ends. ❧ Carbon nanotubes have unique electron ransport properties at high bias voltages. Due to their one dimensional nature, scattering of electrons by phonon are highly nonlinear. At low bias voltages (across the nanotube) phonon scattering is suppressed and the electrons exhibit ballistic transport. At higher bias voltages optical phonon scattering dominates, and subsequently nanotubes heat suddenly. In Chapter 6, the heating of nanotubes is probed using the mechanical vibrations of a carbon nanotube based nanoelectromechanical oscillator. Since the substrate temperature is constant the change in mechanical resonance frequency is attributed to the contraction of the nanotube due to its negative thermal expansion. The bias voltage, at which the mechanical resonance shows a sudden drop, corresponds to experimentally observed optical phonon emission onset voltage for single–walled carbon nanotubes. |
| Keyword | nanotube; thermal expansion; resonator; heating; negative thermal expansion; electron phonon interaction; negative differential conductance; slack resonator; van der Waals; delamination; graphene; platinum |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Contributing entity | University of Southern California |
| Rights | Aykol, Mehmet |
| Physical access | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@dots.usc.edu |
| Archival file | uscthesesreloadpub_Volume4/etd-AykolMehme-1082.pdf |
Description
| Title | Page 1 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@dots.usc.edu |
| Full text | ANALYSIS OF CARBON NANOTUBES USING NANOELECTROMECHANICAL OSCILLATORS by Mehmet Aykol A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (ELECTRICAL ENGINEERING) August 2012 Copyright 2012 Mehmet Aykol |
