Conductance model of gold-molecule-silicon and carbon nanotube-molecule-silicon junctions

We estimate the conductance of molecular junctions composed of an oligo(phenylene ethynylene) (OPE) molecule sandwiched between a metallic gold or carbon nanotube on one end and a semiconducting silicon contact on the other end. Two very well defined, low and high, states of conductance (logic 0 and 1) are obtained through changes in conformation or charge states of the OPE when two metallic contacts address the molecule. However, when a combination of a semiconducting and metallic contacts are used, the bistable states are lost at low bias voltages where a flat region of nearly zero current in the current-voltage characteristic is predicted regardless of the conformation or charge state.