Conductance of Small Molecular Junctions

A new method of fabricating small metal-molecule-metal junctions approaching the single molecule limit is developed. 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 position of these steps can be controlled by a gate potential. The spacing corresponds to energy of lowest molecular vibrations. The results show that the low bias conductance of molecules is dominated by resonant tunneling through coupled electronic and vibrations levels.