Spatially Resolved Tunneling along a Molecular Wire

Building a nano-electronic device using a molecule requires a basic understanding of how a molecular nanowire connects and transports charge from the electrodes. Such a wire can efficiently extend the electrode wave functions, thereby increasing the lateral extension of electron tunneling with a spatial fidelity on the molecular scale. In the experiment described here, the metal wave functions penetrate the molecule from a subnanometer-sized ultraclean electronic contact. This was done using specially designed molecular wires which self-docked onto the edge of a metallic step. High-resolution scanning tunneling microscopy was then used to determine spatially the decay of the
evanescent wave function along the molecule. These results demonstrate a unique, noninvasive method to probe phenomena occurring inside a intramolecular tunnel barrier and the role of electronic coupling to electrodes.