Date of Award

Spring 2005

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Materials Science and Engineering - (Ph.D.)

Department

Committee for the Interdisciplinary Program in Materials Science and Engineering

First Advisor

Haim Grebel

Second Advisor

Zafar Iqbal

Third Advisor

Marek Sosnowski

Fourth Advisor

John Francis Federici

Fifth Advisor

Roger Dorsinville

Abstract

Carbon nanotubes (CNT) and in particular, single-wall carbon nanotubes (SWCNT) have been extensively studied, in large part, due to their unique one-dimensional crystalline structures and related electronic and optical properties. Various polymeric composite materials, which were based on carbon nanotubes, have been also developed in an attempt to combine the properties of polymer and CNT in a single film. Such composites were mainly formed by mixing carbon nanotubes within the polymer without special emphasis on the structure and thereby, the nanoscopic properties of the resultant material.

Photonic crystals belong to a class of man-made structures aimed at manipulating the propagation of electromagnetic waves at sub-wavelength dimensions in the visible range. The objective of this research work was to fabricate optical nano-composites from the bottom up: by incorporating carbon nanotubes within nano-structured templates we attempted to achieve novel composites with unique optical properties.

Three-dimensional photonic crystals were made by self-assembly using monodisperse suspension of silicon dioxide colloids. Upon sedimentation, this highly ordered crystal, also known as opal, serves as a template for polymeric and polymer/CNT composites. For example, by infiltrating of the templates voids with a desired polymeric solution followed by etching of the silica template away, a three-dimensional inverse polymeric structure is obtained.

Single-wall carbon nanotubes (SWCNT) have been directly grown into the template voids (in the range of 20 - 70 nm) by catalytic Chemical Vapor Deposition (CVD) technique with carbon monoxide as the carbon feedstock. The resultant SWCNTs were mostly semiconductive (p-doped). Control over the growth of SWCNT has been obtained by changing the catalyst concentration and the template's void-size.

Various techniques were used to characterize the SWCNT and its composites: Scanning Electron Microscope (SEM) has been used to identify the morphology of structures; interactions between polymer and nanotubes have been characterized by Raman spectroscopy; optical properties were studied by linear and nonlinear optical transmission and optical activity measurements; electrical properties were studied using thermoelectric and photoconductivity measurements. These data suggest that selforganized nano-scale templates are a promising route for realizing novel optical composite materials.

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