A Study on Novel Methods to Improve Conductivity of Carbon Nanotube Films.

摘要

Carbon nanotubes have gained considerable attention in recent years, and have found applications in a variety of fields such as nanotechnology, electronics and optics thanks to their exceptional electrical, optical and mechanical properties. Individual nanotubes have demonstrated extraordinary electron carrying and conducting ability, however, when constructed into networks, the device until this day still fall short of the expectation when being compared with conditional conducting materials. Reasons for this limitation generally include the intrinsic (junctions) and the extrinsic (impurities) ones. Both factors introduce resistance to the electron transport within single walled carbon nanotubes (SWNT) film. In this thesis, three novel methods were adopted in order to tackle those two problems from a different perspective.;Glycolic acid treatment is used to replace traditional strong inorganic acid to target specifically the surfactants trapped inside the network while preserving the structure of SWNT. Glycolic acid was used for both transferred and sprayed processes. In both cases, certain levels of improvement were observed in terms of conducting performance. The decrease in resistance was as high as 11% for sprayed films, and 18% for transferred films. Inconsistency from sample to sample did occur, especially for samples prepared by the membrane transfer technique.;Diffusion activities were examined for metal particles deposited on SWNT networks, establishing the foundation for using metal particles as a medium to improve interjunction electron conduction for SWNT networks. In order to accurately evaluate the degree of diffusion, a novel masking method was developed using NaCl crystallites. The diffusion coefficient and activation energy for Gold particles on the surface of SWNTs films were measured. The behavior can be described as a combination of diffusion of metal particles driven by concentration gradient and metal particles aggregation to reduce surface energy.;9,9-dioctyfluorenyl-2,7-diyl--bipyridine (PFO-BPy) polymer separated semiconducting SWNTs were exposed to Cr(CO)6 in Toluene for the intention of sidewall coherent bonding with Chromium species. The PFO-BPy polymer helps to separate SWNTs therefore providing higher percentage of SWNT surface ready for chemical bonding. Results showed the polymer did effectively break up the bundle and separate the nanotubes; however, the wrapping of the polymer created a barrier to prevent SWNTs from reacting with Cr(CO) 6. The binding between polymers and SWNTs essentially takes away the available locations for the Cr reaction to take place; the higher the concentration of PFO-BPy polymer, the lower the rate of Cr bonding was observed.