Orientation-Controlled Single Molecule-Electrode Junctions
The conductivity of a single aromatic ring, perpendicular to its plane, is determined using a new strategy under ambient conditions and at room temperature using a combination of molecular assembly, Scanning Tunneling Microscopy (STM) imaging and STM break junction (STM-BJ) techniques. The construction of such molecular junctions exploits the formation of highly ordered structures of flat-oriented mesitylene on Au(111) to enable direct tip/π contacts, a result that is not possible via conventional methods. The measured conductance of sandwiched Au/π/Au junction is ~0.1Go, two orders of magnitude higher than the conductance of phenyl rings connected via standard anchoring groups. A comparison with other benzene derivatives, that do not display long-range ordered structure, suggests that such structures, which hold the aromatic ring in place and parallel to the surface, are essential to the increased probability of the formation of orientation-controlled “sandwiched” molecular junctions.