Etched Edge of Metal/Insulator/Metal Pattern for Molecular Scale Contacts

Keywords:
molecular electronics, break junction, electrodes, sensor

Abstract:
Producing reliable electrical contacts with gaps having the dimensions of molecular lengths is a difficult challenge for molecular electronics. As a promising alternative to break-junctions, we use conventional film deposition and photolithography to form an exposed edge of a thin film multilayer structure (metal/insulator/metal). Molecules can self-assemble on the exposed edge offering an alternative conduction path through the molecules with angstrom-scale dimensional control. Critical to this approach is to have minimal background tunnel current between metal planes. We find the role of stresses to be the primary factor in reducing background current Electrodes were successfully fabricated with this strategy with current measured through a metal coordination compound cluster composed of a cube with cyano linked Ni or Fe at the corners. Thiolacetate ligand tethers come off of the cluster core and bind the complex to the metal leads.. Molecules that do not bridge the gap are not electrically active. Along the 10um pattern edge approximately 6000 molecules are involved in conduction. 10nA per molecule is seen at 10mV bias. Tunnel current through the molecules is analyzed with Simmons model and barrier height is found to be 1.1 eV and tunnel length of 1.2nm.

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Nanotech 2006 Conference Program Abstract