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Single-molecule diodes with high rectification ratios through environmental control


Molecular electronics aims to miniaturize electronic devices by using subnanometre-scale active components1,2,3. A single-molecule diode, a circuit element that directs current flow4, was first proposed more than 40 years ago5 and consisted of an asymmetric molecule comprising a donor–bridge–acceptor architecture to mimic a semiconductor p–n junction. Several single-molecule diodes have since been realized in junctions featuring asymmetric molecular backbones6,7,8, molecule–electrode linkers9 or electrode materials10. Despite these advances, molecular diodes have had limited potential for applications due to their low conductance, low rectification ratios, extreme sensitivity to the junction structure and high operating voltages7,8,9,11,12. Here, we demonstrate a powerful approach to induce current rectification in symmetric single-molecule junctions using two electrodes of the same metal, but breaking symmetry by exposing considerably different electrode areas to an ionic solution. This allows us to control the junction's electrostatic environment in an asymmetric fashion by simply changing the bias polarity. With this method, we reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370 mV using a symmetric oligomer of thiophene-1,1-dioxide13,14. By taking advantage of the changes in the junction environment induced by the presence of an ionic solution, this method provides a general route for tuning nonlinear nanoscale device phenomena, which could potentially be applied in systems beyond single-molecule junctions.

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Figure 1: Environmentally enabled single-molecule diodes.
Figure 2: Energy level diagram illustrating the rectification mechanism for a LUMO conducting molecular junction.
Figure 3: High rectification ratios in TDOn junctions.
Figure 4: Rectification with other molecule/solvent systems.
Figure 5: Experimental and computational determination of energy level alignment.


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The authors thank M. Hybertsen and M. Steigerwald for discussions. The experimental work was supported primarily by the National Science Foundation (award no. DMR-1206202). E.J.D. acknowledges the HHMI, the American Australian Association and Dow Chemical Company for International Research Fellowships. The computational work was supported by the Molecular Foundry, and by the Materials Sciences and Engineering Division (Theory FWP), US Department of Energy, Office of Basic Energy Sciences (contract no. DE-AC02-05CH11231). Portions of the computation work were performed at National Energy Research Scientific Computing Center. O.A. acknowledges support from the NSF (award no. DMR-1122594). L.V. thanks the Packard Foundation for support.

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Experiments were conceived and designed by B.C., O.A., L.M.C., J.B.N. and L.V. and performed by B.C., O.A. and J.C.T. Data analysis was carried out by B.C. and O.A. Compounds were synthesized by J.L. and E.J.D. Calculations were performed by Z-F.L. and J.B.N. The manuscript was co-written by B.C., J.B.N., L.M.C. and L.V., with input from all authors.

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Correspondence to Jeffrey B. Neaton, Luis M. Campos or Latha Venkataraman.

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The authors declare no competing financial interests.

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Capozzi, B., Xia, J., Adak, O. et al. Single-molecule diodes with high rectification ratios through environmental control. Nature Nanotech 10, 522–527 (2015).

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