A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. / A comprehensive experimental study on alternating current (AC) electrical transport in the three forms of carbon nanotubes (CNTs) and nanodiamond films is presented. It is termed dynamic electrical transport to differentiate it from direct current measurements, which may be referred as static transport. The results and analysis are based on the scattering parameter measurements of a few horizontally aligned single, double, multi-walled carbon nanotubes and nanodiamond films. Which were measured in the frequency range 10 MHz to 65 GHz, at room and cryogenic temperatures using a vector network analyser. The work is motivated by the fact that AC transport in 1D systems has not been fully studied and is not well understood. From direct current measurements, it is known that one dimensional (1D) electrical transport is very different from its two or three dimensional counterpart. This is because adding an electron to a 1D system tends to affect the whole system in ways which to date cannot be fully explained theoretically. CNTs present an ideal platform to study the AC or dynamic transport behaviour of 1D systems because of the high mobility and electrical conductivity at nano-scale. Therefore from the AC complex impedance and conductance, this work demonstrates quantum effects of collectively excited strongly interacting electrons (Luttinger Liquid), which had been predicted theoretically but not observed experimentally using this technique. Ballistic transport at room temperature is also demonstrated by setting the stimulus frequency higher than the scattering rate in the CNTs. A crossover from capacitive to inductive behaviour in the imaginary component of impedance has been shown by improving the CNT-electrode coupling. Furthermore the effect of metal contacts on microwave/ radio frequency transmission is also demonstrated. The results are consolidated by RF simulations, as strong conclusions are drawn. Studies on the dynamic transport in nanodiamond films revealed a crossover from the insulating to semi-metallic regime by nitrogen incorporation. The crossover is explained by considering the changes of the grain boundary morphology. This work shows that AC transport in polycrystalline nanodiamond films is similar to DC transport.

Current research in the field of nano-electronics is directed towards device miniaturization in order to find ways to increase the speed of electronic devices. The work presented in this dissertation is on the electronic transport properties of single walled carbon nanotube (SWNT) ropes synthesized by laser ablation. The measurements were performed on devices with different geometries; namely SWNT mats, metal incorporated (aligned individual and bundled) SWNTs and lastly on aligned pure SWNTs from low temperatures up to room temperature. The work was performed so as to gain an understanding on how best to utilize SWNTs in the semiconductor industry towards miniaturization. Such an understanding would ultimately highlight if SWNTs can be considered as a viable alternative to the current silicon-based technology, which seems to be approaching its physical limit. For a mat of SWNTs, 3D-Variable range hopping is the principal conduction mechanism from 2 K – 300 K. The magneto-resistance was found to be predominantly negative with a parabolic nature which converts to a linear nature as the temperature is increased. The negative MR is a consequence of quantum interference and the positive upturn is attributed to wave function shrinkage at low temperatures as described by the Efros-Shklovskii model. The hopping ranges of the electrons for a SWNT mat increases as the temperature decreases due to manifestation of quantum effects and reduced scattering. It was also found that metal incorporation does not alter the properties of the SWNT significantly. SWNT ropes aligned by di-electrophoresis across a 1 micron gap between gold micro-electrodes, exhibit Tomonaga-Luttinger liquid (TLL) like behaviour, within the 80 K – 300 K temperature range. The effects of confinement and electron-electron interaction unique to one dimension were identified in electronic transport as a non-universal power law dependence of the differential conductance on temperature and source-drain voltage. Ballistic conductance at room temperature was confirmed from the high frequency transport of the SWNT devices. The complex impedance showed some oscillatory behaviour in the frequency range 6 to 30 GHz, as has been predicted theoretically in the Tomonaga-Luttinger Liquid model. The observation of Luttinger Liquid behaviour demonstrates the outstanding nature of these one-dimensional molecular systems. In these devices the charging Coulomb energy of a single particle played a critical role in the overall device performance. This study can be used to understand the nature of dynamics of plasmons which are the charge carriers in a TLL system and how Coulomb interactions can be used to design highly tuneable systems for fabrication of single molecule devices. The incorporation of metal onto individual SWNT ropes does not alter its electronic properties significantly but the properties of the bundled metal incorporated SWNT ropes are altered. This study has found that under optimized conditions SWNTs might be a viable option for incorporation in nano electronics devices. Individual SWNT ropes promise better devices compared to SWNT mats and further work should be done on individual SWNTs.

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by Jia, Jiangying. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves ). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.ii / ACKNOWLEDGEMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.vii / LIST OF TABLES --- p.ix / Chapter CHAPTER ONE --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.1.1 --- Vibration damping --- p.2 / Chapter 1.1.2 --- Carbon nanotubes --- p.4 / Chapter 1.1.3 --- Fabrication of carbon nanotube composites --- p.8 / Chapter 1.1.4 --- Literature review on carbon nanotube composites --- p.10 / Chapter 1.2 --- Research Objective --- p.13 / Chapter 1.3 --- Thesis Organization --- p.14 / Chapter CHAPTER TWO --- FABRICATION OF CNT AND CNT/EPOXY COMPOSITES --- p.15 / Chapter 2.1 --- Fabrication of CNT --- p.16 / Chapter 2.1.1 --- Fabrication requirements --- p.16 / Chapter 2.1.2 --- Substrate and catalyst preparation --- p.17 / Chapter 2.1.3 --- Aligned CNT film grown by PECVD method --- p.18 / Chapter 2.2 --- Fabrication of CNT/Epoxy Composite --- p.25 / Chapter 2.3 --- Measurement of CNT/Epoxy Composites --- p.31 / Chapter 2.4 --- Chapter Summary --- p.34 / Chapter CHAPTER THREE --- MODELLING OF THE CNT COMPOSITES --- p.35 / Chapter 3.1 --- Geometrical Configuration of Composites --- p.36 / Chapter 3.2 --- Critical Shear Stresses and “Stick-Slip´ح Behavior --- p.38 / Chapter 3.3 --- Nonlinear Viscoelastic Composite Model --- p.40 / Chapter 3.3.1 --- Maxwell model --- p.40 / Chapter 3.3.2 --- Three-parameter standard solid model --- p.45 / Chapter 3.4 --- Stress and Strain Evaluation --- p.50 / Chapter 3.5 --- Effective Moduli and Loss Factor of Composite --- p.56 / Chapter 3.6 --- Chapter Summary --- p.60 / Chapter CHAPTER FOUR --- PARAMETRIC STUDY OF THE CNT COMPOSITES --- p.61 / Chapter 4.1 --- Carbon Nanotube Dimensions --- p.62 / Chapter 4.2 --- Parametric Study --- p.65 / Chapter 4.3 --- Summary --- p.69 / Chapter CHAPTER FIVE --- CONCLUSIONS AND FUTURE WORK --- p.70 / Chapter 5.1 --- Conclusions --- p.70 / Chapter 5.2 --- Future Work --- p.72 / BIBLIOGRAPHY --- p.73 / APPENDIX --- p.78 / Chapter A. --- Epoxy Resin Datasheet --- p.78 / Chapter B. --- Matlab Program for Young´ةs Modulus Calculation --- p.80 / Chapter C. --- Matlab Program for Loss Factor Calculation --- p.82

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: Chin-Pao Huang, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

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Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 41-42) Also available in print.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references. Also available in electronic version.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2009. / Includes bibliographical references.

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 74-77).