Synthesis and characterization of vertical and horizontal nanowires for functional device fabrication
Nanotechnology is a design, synthesis and implementation of nanostructures or nanomaterials. It paves a way for fundamental understanding of materials’ dimension and their corresponding physical properties for a desired application. Synthesis and processing of nanostructures are the essential aspects of nanotechnology. Studies on their new physical properties and applications are possible only when nanostructured materials are made available with desired size, morphology, microstructure and chemical composition. In general, there are two philosophically distinct approaches for creating small objects: top-down and bottom-up. In the top-down approach, small features are patterned in bulk materials by a combination of lithography, etching and deposition to form functional devices and their integrated systems. The top-down approach has been exceedingly successful in many venues, with perhaps, microelectronics being the best example today. While developments continue to push the resolution limits of the top-down approach, these improvements in resolution are associated with a near exponential increase in cost associated with each new level of manufacturing facility. Whereas, in the bottom-up approach the functional structures are assembled from well defined chemically and/or physically synthesized nanoscale building blocks. The optimization of this bottom-up approach for nanotechnology requires a focus on two key areas that are at the heart of devices and integration processes. First of all, the bottom-up approach necessitates nanoscale building blocks with precisely controlled and tunable chemical composition, structure, size and morphology, as these characteristics determine their corresponding physical properties. To meet this goal, it requires developing methods that enable rational design and predictable synthesis of building blocks. Secondly, it is critical to explore and developthe limits of functional devices based on these building blocks. In this doctoral work, the above basic principles are taken into consideration for the selection of both vertical and horizontal nanowire fabrication techniques, the integration of the synthesized functional nanowires into device and their characterization under different conditions.