Solution Processable Nanostructures for Molecular Electronics
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In molecular electronics, the building material (traditionally elemental semiconductor) is replaced by single molecules or a nanoscale collection of molecules. Key to molecular electronics is the ability to precisely embed molecules into a nano device/structure and to manipulate large numbers of functional devices so they can be built in parallel, with each nano-device precisely located on the electrodes. In this work, the assembly of organic and inorganic nanostructures dispersed in aqueous solutions has been controlled via chemical functionalisation. By combining this bottom-up assembly strategy with traditional top-down lithographic apporaches, the properties of these nanostructures have been investigated via a range of different techniques. The high degree of control on the molecular design through chemical synthesis and the scalability by self-assembly make this approach of interest in the field of molecular electronics. In this regard, this dissertation presents a solution-based assembly method for producing molecular transport junctions employing metallic single-walled carbon nanotubes as nanoelectrodes. On solid substrates, electrical and electronic properties have been investigated by Conducting Atomic Force Microscopy (C-AFM). Furthermore, different strategies for asymmetric junction formation have been explored towards the development of a potential nanoscale Schottky diode. Moreover, various patterning techniques based on shadow evaporation and AFM probe scratching have been investigated for the assembly of 1-D nanostructures. Nanostructures dispersed in solution were organised onto surfaces by means of dielectrophoretic assembly, and their electronic properties was then measured by the means of a probing station. In addition to the aforementioned organic nanostructures, we also report on the dispersion of boron nitride nanotubes (BNNT) by DNA wrapping, followed by the formation of nano-hybrids of boron nitride nanotubes and carbon nanotubes. Previously, researchers have adopted BNNT as a 2D dielectric layer. The work inspires me to adopt boron nitride nanotubes as 1D dielectric materials. The techniques developed in this thesis are of interest for fundamental studies of electron transport in molecules and nanostructures. Addtionally, the approaches developed in this work may facilitate the advancement of new technologies for electronics, including, but not limited to, future circuits based on single-wall carbon/boron nitride nanotubes with specific functionality.
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