A simple procedure for fabricating molecular-sized gap junctions using conventional photolithography

We describe a procedure for fabricating sub-5 nm gap junctions with sub-100 nm electrode-width using conventional photolithography. The fabrication procedure involves two photolithographic processes followed by shadow evaporation and electromigration. After lift-off following the second metal shadow evaporation, a nanoscale wire with a diameter less than 100 nm is fabricated along a sidewall of the second patterned photo-resist. The nanowire is cut by a milliamp current flow, then a sub-5 nm gap metal junction with a sub-100 nm electrode-width is fabricated. The temperature dependence of the conductance of the molecular wires that were bridging the junctions over the ultrasmall gap indicated a hopping conduction behaviour. The results demonstrate that these junctions can be used in the study of conductance measurements through molecular wires.