Design, synthesis, and testing of novel organic oligomers for use as molecular-scale electronic devices
Flatt, Austen Kyle
Tour, James M.
Doctor of Philosophy
Based on rational design principles, diverse arrays of small organic oligomers containing unique electronics structures and redox functionalities have been synthesized for use in molecular-scale electronic device architectures. Thiol terminated oligoanilines were found to exhibit reproducible bistable switching behavior with an on-off ratio of > 10:1 at room temperature when biased between metal electrodes. The synthesis of orthogonally functionalized oligomers has resulted in compounds containing functionalities on one end known to form ordered self-assembled monolayers on metal surfaces while at the other end an intact thioacetate is present whereby self-assembly may again occur after an in situ deprotection for use in NanoCell electronic memories. The NanoCell devices were found to exhibit switching behavior when biased, with a two state memory; however the switching proved to be metallic in nature. Additionally, orthogonally functionalized oligomers allow for the covalent attachment of carbon nanotubes to silicon surfaces for possible uses in sensor and electronic device embodiments. This technique relies on the ability to graft aryldiazonium salts onto a silicon hydride passivated surface followed by diazotization of the terminal aniline. Organic aryltriazenes have been shown to assemble on hydride passivated silicon surfaces by using an in situ diazotization protocol in dilute HF solution. Film thicknesses range from a monolayer to 200 nm depending on conditions. Novel U-shape oligomers have been synthesized to aid in the elucidation of molecular switching behavior and monolayer film formation using advanced surface characterization techniques. These conformationally restricted oligomers are designed to be of use in studies utilizing scanning probe microscopy techniques to elucidate switching mechanisms and negative differential resistance behavior thought to be based on molecular conformational changes.