Description:

This is a scanning electron microscope picture of the lithographically fabricated break junction. The setup consists of a metallic plate, covered by an insulating layer of polyimide. On top of this, a gold film with a small constriction (smallest diameter 50 3 50 nm2) is deposited, laterally structured by e-beam lithography. Two electrodes lead outside to connect the bridge electrically. The polyimide is partially etched away so that in the constriction region, the bridge is freely suspended over the polyimide substrate.

This group has been investigating electronic transport through two types of conjugated molecules. Mechanically controlled break junctions are used to couple thiol (sulfur-basee) end groups of single molecules to two gold electrodes.  Current-voltage characteristics (IVs) of the metal- molecule-metal system are observed. These IVs reproduce the spatial symmetry of the  molecules with respect to the direction of current flow. They, hereby unambiguously  detect an intrinsic property of the molecule and are able to distinguish the influence of both the molecule and the contact to the metal electrodes on the transport properties of the compound system.
 

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