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Molecular Logic for Nanoelectronics

Following the successful demonstration (Nature 2007, 445, 414???417) of a working defect-tolerant 160,000 bit molecular memory composed of a Langmuir-Blodgett (LB) derived monolayer of amphiphilic, bistable rotaxane molecules and fabrication in a crossbar architecture with nanowires (15 nm wide polysilicon underneath and 15 nm wide Ti/Al on top sandwiching approximately 200 molecules) at a density (1011 bits cm-2) not predicted, according to the 2005 International Technology Roadmap for Semiconductors (2005 ITRS), to be reached until 2020 at the earliest, the aim of this research project is to design and synthesize, by template-directed protocols that depend upon the operation of molecular recognition and self-assembly processes, bistable rotaxanes, which are amphiphilic or functionalized for carrying out Huisgen/Sharpless-style ???click chemistry??? with matching electrode surfaces, and undego a change in their dipole moments in response to an electrochemical stimulus that causes relative mechanical motions to occur within the bistable rotaxane molecules. Monolayers of these molecules will then be assessed in a device setting which involves a two-terminal molecular switch tunnel junction (MSTJ) to establish whether or not they can be switched electrically between high and low capacitance states, and hence, in principle at least, can serve as active reconfigurable channels in logic circuits. The research objectives will be reached by controlling the nature and location of the charged components in these nanoelectromechanical systems (NEMS) where control of the dielectric properties of monolayers of these bistable molecules will be achieved through dipole induction and/or charge-storage processes. The compounds that are designed to address reconfigurable molecular logic will also feature a unique collection of recognition units which could be employed to expand the available chemical space for a much wider range of applications addressable by artificial molecular machinery.