A new paradigm for molecular electronics is based on conjugated, covalent bonding between an organic monolayer and a graphitic carbon substrate. The low injection barrier between the graphite and monolayer appears to result in an ohmic contact, and the strong C-C bond results in thermally stable monolayers (to 400 °C) which can withstand vapor deposition of a metallic top contact. The resistance of carbon based molecular junctions is strongly dependent on molecular structure and length, and junctions in the range of 5-50 Å thickness have been studied so far. A possibly important phenomenon common to several junction types is conductance switching, in which a junction may be repeatedly switched between high and low conductivity states. ON/OFF ratios of 10-100 have been observed so far, and switching is repeatable thousands of times for selected monolayer molecules. The mechanism of conductance switching will be discussed, as will its possible application as a low-power nonvolatile memory element.
Srikanth Ranganathan, Ilson Steidel, Franklin Anariba, Richard L. McCreery, "Covalently Bonded Organic Monolayers on a Carbon Substrate: A New Paradigm for Molecular Electronics", Nano Letters, 2001, 1 (9), 491- 494.