Gated molecular devices using self-assembled monolayers

A new method of fabricating small metal–molecule–metal junctions is developed, approaching the single-molecule limit. The conductance of different conjugated molecules in a broad temperature, source–drain and gate voltage regime is reported. At low temperature, all investigated molecules display sharp conductance steps periodic in source–drain voltage. The positions of these steps can be controlled by a gate potential. The spacing corresponds to the energy of the lowest molecular vibrations. These results show that the low bias conductance of molecules is dominated by resonant tunnelling through coupled electronic and vibration levels.