Developing Longer-Lived Single Molecule Junctions with a Functional Flexible Electrode.

Creating single-molecule junctions with a long-lived lifetime at room temperature is an open challenge. Finding simple and efficient approaches to increase the durability of single-molecule junction is also of practical value in molecular electronics. Here it is shown that a flexible gold-coated nanopipette electrode can be utilized in scanning tunneling microscope (STM) break-junction measurements to efficiently enhance the stability of molecular junctions by comparing with the measurements using conventional solid gold probes. The stabilizing effect of the flexible electrode displays anchor group dependence, which increases with the binding energy between the anchor group and gold. An empirical model is proposed and shows that the flexible electrode could promote stable binding geometries at the gold-molecule interface and slow down the junction breakage caused by the external perturbations, thereby extending the junction lifetime. Finally, it is demonstrated for the first time that the internal conduit of the flexible STM tip can be utilized for the controlled molecule delivery and molecular junction formation.