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M.S. Defense Tuesday, June 19, 2007 Room 203 ENG II 1:00PM Title: Assembly of Single-walled Carbon Nanotube-Quantum Dot-Single-walled Carbon Nanotube Heterostructures: Structural and Electrical Characterization Abstract: The fabrications of single-walled carbon nanotube-quantum dot-single-walled carbon nanotube (SWNT-QD-SWNT) heterojunctions, along with the structural and electrical characterizations, are described in this research. Varies types of assemblies with different nanostructures have been developed in the past, such as CNT-QD and CNT-DNA. However, electrical characterizations have yet to be studied with SWNT-QD assemblies. A two-step procedure was described to synthesize the SWNT-QD-SWNT assemblies. The efficiency of producing successful assemblies and the electrical characterizations were studied using the tapping and TUNA (Tunneling AFM) mode with AFM, respectively. With the technology of TUNA, electrical measurements were able to be executed at specific sites on the sample. A couple of procedures of QD functionalization were discussed to illustrate an amine-functionalized QD versus a carboxyl QD. A number of different techniques, such as Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), have been utilized to image the topography of these nanostructures. One major drawback to SEM is that it only works well with conducting materials or materials coated with a conducting element. In addition, the high intensity of the electron beam may cause localized sites to become charged, and hence contaminate the original and unique electrical property of the sample. As a result, atomic force microscopy (AFM) was used extensively to analyze the topography and electrical properties of the heterostructures. A few isolated SWNT-QD-SWNT samples were found and investigated to differentiate one nanostructure from another and the unique electrical properties each of them possessed. Depending on the unique electrical properties of the assemblies, ultimately, they can be used in the fabrication to provide a higher efficiency and hopefully cost-effective means in the semiconductor industry. |
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