| Ongoing miniaturization in integrated circuit (IC) device fabrication via conventional lithography faces increasing technical challenges and imposes significant performance limitations on devices and interconnects stemming from the fundamental physics of electron transport. This drives the need to explore other nanofabrication approaches, such as self-assembly, and alternate device or interconnect structures with novel electron transport mechanisms, such as ballistic electron transport. Molecular self-assembly, ubiquitous in biology and bio-inspired materials, might have tremendous potential for nanoelectronic applications. Specifically, genetically-engineered beta-sheet polypeptides offer certain key attributes for nanoelectronic applications. These attributes include: controllable self-assembly, potential to form one dimensional quantum channels for ballistic electron transport, and substrate-specific interactions for interfacial engineering. This dissertation explores and evaluates the nanowire self-assembly characteristics of several de novo genetically-engineered beta-sheet polypeptides (synthesized by our group) on various substrates for applications in nanoelectronic interconnect schemes. In addition, substrate-attachment of the beta-sheet polypeptide nanowire structures is investigated and preliminary electrical testing of a polypeptide nanowire fibril is presented. Chapters 1 and 2 provide an overall introduction and discuss the characterization techniques utilized in the experimental work. Chapter 3 describes a detailed self-assembly study of various polypeptides and documents the formulation and deposition of controlled, linear self-assemblies of polypeptides. It was determined that control of the concentration and deposition-time enables the deposition of linear ordered polypeptide assemblies on substrates. A predominance of bilayer stacking of polypeptide sheets in the solution-formed linear assemblies has been observed. Template-directed self-assembly of linear polypeptide assemblies has also been documented on graphite surfaces. This has demonstrated the potential for epitaxial or template-directed ordering of polypeptides on substrates for potential nanoelectronic applications. Chapter 4 describes an adhesion study of polypeptide nanostructures on various substrates. A forced-scanning methodology based on atomic force microscopy was employed and used to identify specific (covalent) and non-specific (physisorbed) interactions of the polypeptide to a variety of substrates. This information is important for substrate and electrode attachment of polypeptides for nanoelectronic applications. Chapter 5 presents the results of scanning tunneling microscopy of polypeptide monolayers on graphite and theoretical charge density calculations. These results confirm that this polypeptide exhibits a beta-sheet conformation on the graphite substrate. |
