Molecular-scale components are expected to be central to the realization of nanoscale electronic devices1,2,3. Although molecular-scale switching has been reported in atomic quantum point contacts4,5,6, single-molecule junctions provide the additional flexibility of tuning the on/off conductance states through molecular design. To date, switching in single-molecule junctions has been attributed to changes in the conformation or charge state of the molecule7,8,9,10,11,12. Here, we demonstrate reversible binary switching in a single-molecule junction by mechanical control of the metal–molecule contact geometry. We show that 4,4'-bipyridine–gold single-molecule junctions can be reversibly switched between two conductance states through repeated junction elongation and compression. Using first-principles calculations, we attribute the different measured conductance states to distinct contact geometries at the flexible but stable nitrogen–gold bond: conductance is low when the N–Au bond is perpendicular to the conducting π-system, and high otherwise. This switching mechanism, inherent to the pyridine–gold link, could form the basis of a new class of mechanically activated single-molecule switches.
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We thank C. Wiggins and P. Kim for discussions. Portions of this work were performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, and were supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy. This work was supported in part by the Nanoscale Science and Engineering Initiative of the NSF (award numbers CHE-0117752 and CHE-0641532), the New York State Office of Science, Technology and Academic Research (NYSTAR) and the NSF Career Award (CHE-07-44185) (M.K. and L.V.). This work was supported in part by the US Department of Energy, Office of Basic Energy Sciences, under contract number DE-AC02-98CH10886 (M.S.H.). H.J.C. acknowledges support from KISTI Supercomputing Center (KSC-2007-S00-1011). Computational resources from NERSC are acknowledged.
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Quek, S., Kamenetska, M., Steigerwald, M. et al. Mechanically controlled binary conductance switching of a single-molecule junction. Nature Nanotech 4, 230–234 (2009). https://doi.org/10.1038/nnano.2009.10
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