Electronics and Mechanics of Single Molecule Circuits

The field of molecular electronics involves probing, manipulation, and control of single molecules as active elements in electrical circuits. The underlying focus is to fabricate single molecule circuits,  molecule attached to two electrodes, with varied functionality, where the circuit structure is potentially defined with atomic precision. An experimental prerequisite to creating functional molecular devices is to fabricate single molecule junctions reliably and understand their physical properties. In this talk, I will review the scanning tunneling microscope break-junction technique we use to measure electronic transport through single molecule junctions, and focus on electron transport in the linear response regime. I will discuss our measurements using novel metal-molecule link chemistries including amine-gold, methyl sulfide-gold and dimethyl phosphine-gold to demonstrate the influence of the intrinsic molecular properties, including their length, conformation, the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and the alignment of this gap to the metal Fermi level on the measured conductance. I will then show some recent results where we demonstrate reversible binary switching in a single-molecule junction by mechanical control of the metal-molecule contact geometry.