Electrochemical NanoScience Group
‹— Nanostructures | ‹— Research topics

Electrochemical approach to Molecular Electronics

Scanning tunneling spectroscopy (STS) is an important technique in Scanning Tunneling Microscopy (STM) to probe the local electronic information of the sample surface. The single molecular conductance can be measured by the repeated formation and breaking of molecular junctions between an STM tip and a substrate modified with the specific molecule. Each breaking event is revealed as a step in the current-distance curve. The statistical analysis of the individual traces allows the determination of the conductance of single molecular junctions.

In electrochemical controlled STM configurations, substrate and tip electrodes, equivalent to source and drain electrodes in a transistor, are operated in bipotentiostatic mode. Their potentials are independently controlled by a common reference electrode. The latter acts as an electrochemical “gate” and modulates the tunneling current between source and drain (substrate and tip) electrodes. Since the gate voltage falls across the double layers at the electrode-electrolyte interfaces, the effective gate thickness is of the order of a few solvated ions, which results in a large gate field. In this way, it could be seen from EC-IV characterization that redox-active molecules in the tunneling gap can be brought to display transistor and/or diode characteristics.
Metal nanocontact

Single molecule junction

Resonant tunneling

gold 111 conductance histogram nonanedithiol conductance histogram resonant tunneling enchancement
Revised: 11.12.2007     ©: 2005-2007