NIRT: Field Effect Switching of Molecular Charge Configurations for QCA

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NIRT: Field-effect switching of molecular charge configuration for QCAThis proposal was received in response to Nanoscale Science and Engineering initiative, NSF 03-043, category NIRT. Single-molecule quantum-dot cellular automata (QCA) cells are realized by designing molecules with multiple redox centers. The distribution of molecular charge among the redox centers represents binary information. The key to QCA behavior is that a local electric field, the "driver field," due to a neighboring molecule alters the charge configuration of another molecule in a nonlinear way. Demonstration of field-effect switching of molecular charge configuration is the focus of the proposed research. The use of scanning probes with molecular resolution is crucial to this investigation. Our strategy is to use chemical variation of mixed-valence pieces to remove any ambiguities in the interpretation of our results. Shrinking electronic devices to the single-molecule level may require abandoning the notion of using transistors to represent binary information. The research is exploring a different approach - using molecules, which can exist in two different configurations to encode the binary information. This approach, called quantum-dot cellular automata (QCA), has already been demonstrated at a larger length scale using small metal dots. We are investigating one aspect of a molecular QCA implementation - the switching of one molecule by the influence of a neighboring molecule. This problem is at the heart of the molecular QCA concept, which if successful would enable device densities perhaps a million times greater than those possible with silicon transistors.