Achieving Molecular Level Control over the Chemical, Electrochemical, and Electrical Properties of Crystalline Si Surfaces

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In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Nathan Lewis of the California Institute of Technology will develop methods for the modification of Si surfaces that allow for control over the direction, degree of, and chemical form of, charge flow across such interfaces. The approach is to develop and demonstrate chemically based methods that will allow the deposition of metals onto Si without formation of metal silicides; to demonstrate chemical methods to utilize conducting polymers as the charge acceptor, instead of metallic electrocatalyst particles, to accommodate charge flow without metal silicide formation; and to elaborate methods that will allow manipulation of the physical placement of conductive metal particles based on light-directed surface functionalization of Si, so that catalysts can be placed directly where the charges are flowing across interfaces. The development of systems that control interfacial charge flow will address some of the key barriers presented by actual use of Si surfaces in several critically important applications. Other broader impacts involve training graduate students and postodcotral researchers in interdisciplinary surface and energy sciences, broadly disseminating research results and concepts in publications and scientific presentations as well as TV, radio and electronic media interviews, and educational outreach via the Caltech Chemistry Animation Project.Chemical modification of silicon surfaces is important in interfacing with silicon-based circuitry, developing novel chemical sensors, and obtaining higher efficiencies from existing photovoltaic cells, among many applications. The goal of this work is to develop structure-function relationships for such surfaces and to demonstrate new and beneficial device behaviors that are enabled by virtue of having molecular level control over the chemistry the silicon surface. Of specific interest in the proposed work is the control over silicon surfaces in contact with electron conductors, including metals, conducting polymers, and other charge acceptors.