Reconnectable Sub-5 nm Nanogaps in Ultralong Gold Nanowires

A protocol is described for forming reconnectable sub-5 nm nanogaps in single ultralong (>100 microm) gold nanowires fabricated by lithographically patterned nanowire electrodeposition (LPNE). During an initial computer-controlled electromigration process, gold nanowires with a rectangular cross-section were transformed by the formation of a constriction at a single point along the 250 microm length of the nanowire, and within this constriction a nanogap of width <5 nm. After this initial nanogap formation, 42% (19 of 45) of the gaps could be reconnected by applying a voltage ramp, restoring the electrical resistance of the original nanowire to within 10%. The voltage threshold for nanogap reconnection was narrowly distributed across multiple wires and nanogaps and in the range from 2 to 3 V. Using voltage programming, it was possible to cycle between the open and closed states for some nanogaps more than 100 times. We propose that the mechanism for reconnection involves the field evaporation of gold, qualitatively as observed previously for metal transfer from the tip of a scanning tunneling microscope.