Highly conductive single molecular junctions by direct binding of π-conjugated molecule to metal electrodes

We have investigated electrical conductance of the single C60 and benzene molecules bridging between metal electrodes. The single C60 and benzene molecular junctions were prepared in ultra high vacuum. The single molecular junctions showed the high conductance values (around 0.1-1 G0: G0 = 2e2/h), which were comparable to that of the metal atomic contact. The highly conductive single molecular junctions could be prepared by direct binding of the π-conjugated organic molecule to the metal electrodes without the use of anchoring groups. For comparison, the single 1,4-benzenediamine molecular junction was investigated in solution. The benzene molecule was bound to the Au electrodes via amine (anchoring group) for the single 1,4-benzenediamine molecular junction. The conductance of the single 1,4-benzenediamine molecular junction was 8 x 10-3G0. It was suggested that the anchoring groups acted as resistive spacers between the molecule and metal.