I/V characteristics recorded in mechanically controllable break junctions revealed that field emission transport is enhanced in single molecule junctions as the gap size between two nanoelectrodes is reduced. This observation indicates that Fowler-Nordheim tunneling occurs not only for intermolecular but also for intramolecular electron transport driven by a reduced energy barrier at short tunneling distances.

A bridged version: Molecular junctions bridged by metal ion complexes were investigated by mechanically controllable break junction experiments on the level of individual molecules. The electrical conductance of the junctions varied strongly with the kind of bonded metal ion, in the order: Ca2+≫Zn2+>Ni2+ (see figure).