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Dielectrophoresis has been used as a technique for the parallel localization and alignment of both semiconducting and metallic carbon nanotubes (CNTs) at junctions between electrodes. A variation of this technique known as Floating Potential Dielectrophoresis (FPD) allows for a self-limiting number of CNTs to be localized at each junction, on a massively parallel scale. However, the smallest FPD geometries to date are restricted to conductive substrates and have a lower limit on floating electrode size. We present a geometry which eliminates this lower limit and enables FPD to be performed on non-conducting substrates. We also discuss experiments clarifying the self-limiting mechanism of CNT localization and how it can be used advantageously as devices are scaled downward to smaller sizes.

Massively parallel arrays of single walled carbon nanotubes (SWNT) have attracted significant research interests because of their ability to (i) average out inhomogeneities of individual SWNTs, (ii) provide larger on currents, and (iii) reduce noise to provide higher cutoff frequency for radio frequency applications. However, the array contains both metallic and semiconducting SWNTs and the presence of metallic nanotube in an aligned array negatively affects the device properties. Therefore, it is essential to selectively remove metallic nanotubes to obtain better transistor properties. It was recently found that although such a selective removal can be effective for a low density array, it does not work in a high density array and lead to a correlated breakdown of the entire array giving rise to a nanofissure pattern. In order to obtain a deeper understanding of such a correlated SWNT breakdown, we studied the breakdown power in the successive electrical breakdown of both low ( < 2 /um) and high density ( > 10 /um) SWNT arrays. We show that the breakdown voltage in successive electrical breakdown increases for low density array while it decreases for high density arrays. The estimated power required for the breakdown remains constant for low density arrays while it decreases for high density arrays in successive electrical breakdowns. We also show that, while a simple model of parallel resistor network can explain the breakdown of low density array, it cannot explain the behavior for the high density array implying that the correlation between the closely spaced parallel nanotubes plays a big role in the successive breakdowns of the high density SWNTs.

Conjugated tetrazine-containing polymers that undergo Inverse Electron Demand Diels-Alder (IEDDA) reactions with trans-cyclooctenes are interesting not only for their intrinsic optoelectronic properties, but also their interactions with π-conjugated surfaces. Here, we prepared a series of poly(fluorene-co-tetrazine) polymers and carried out IEDDA reactions to decorate them with hydroxyl, hexadecyl, or triethylene glycol side chains. The polymers were investigated pre- and post-IEDDA coupling in terms of their ability to disperse single-walled carbon nanotubes (SWNTs) in organic solvent. It was found that polymer molecular weight, side chain structure, and degree of conjugation all impacted the quality of SWNT dispersions. While the starting poly(fluorene-co-tetrazine) polymer produced concentrated dispersions, the post-IEDDA polymer containing dihydropyridazine groups did not produce dispersions of equal concentration. However, upon oxidation to the fully aromatic pyridazines, the polymers regained their ability to form concentrated dispersions. Furthermore, the post-IEDDA polymers exhibited increased selectivity toward metallic SWNTs relative to the starting polymer. In addition, due to the efficiency of the IEDDA reaction, it was possible to perform modification of the polymer-SWNT dispersion formed with poly(fluorene-co-tetrazine) to modify the polymer structure while on the SWNT surface. Overall, this work demonstrates the first use of reactive polytetrazines to disperse SWNTs and to rapidly modify the solubility of polymer-nanotube complexes. / Thesis / Master of Science (MSc)

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