Molecular wires, switches, and memories.

Design and measurements of molecular wires, switches, and memories offer an increased device capability with reduced elements. We report: Measurements on through-bond electronic transport properties of nanoscale metal-1,4-phenylene diisocyanide-metal junctions are reported, where nonohmic thermionic emission is the dominant process, with isocyanide-Pd showing the lowest thermionic barrier of 0.22 eV; robust and large reversible switching behavior in an electronic device that utilizes molecules containing redox centers as the active component, exhibiting negative differential resistance (NDR) and large on-off peak-to-valley ratio (PVR) are realized; erasable storage of higher conductivity states in these redox-center-containing molecular devices are observed; and a two-terminal electronically programmable and erasable molecular memory cell with long bit retention time is demonstrated.

Synthesis and preliminary testing of molecular wires and devices.

Presented here are several convergent synthetic routes to conjugated oligo(phenylene ethynylene)s. Some of these oligomers are free of functional groups, while others possess donor groups, acceptor groups, porphyrin interiors, and other heterocyclic interiors for various potential transmission and digital device applications. The syntheses of oligo(phenylene ethynylene)s with a variety of end groups for attachment to numerous metal probes and surfaces are presented. Some of the functionalized molecular systems showed linear, wire-like, current versus voltage (I(V)) responses, while others exhibited nonlinear I(V) curves for negative differential resistance (NDR) and molecular random access memory effects. Finally, the syntheses of functionalized oligomers are described that can form self-assembled monolayers on metallic electrodes that reduce the Schottky barriers. Information from the Schottky barrier studies can provide useful insight into molecular alligator clip optimizations for molecular electronics.