Feedback controlled break junction in Au-Ag-Au nanowires

Fabrication of on-chip nanogap electrodes suitable for molecular electronics applications has long been interest and technological challenge to scientist. Electromigration is one of the most feasible means of making nanoscale metallic junctions between microscopically defined measurement pads. Lithographically defined thin Au wires with notch are the most common templates for feedback-controlled electromigration which can form break junctions in the order of a few nanometers to 30 nm, depending on the material properties, DC ramp and environmental conditions. We proposed using striped Au nanowires with a tiny Ag segment in the middle at which current flow induced migration of atoms may create voids and eventually a gap during feedback-controlled DC ramping. 7 micrometer long 320 nm diameter Au-Ag-Au nanowires having only 30 nm long silver strip were synthesized using electrodeposition and aligned across lithographically defined electrode pairs vi AC dielectrophoresis. We used a feedback algorithm involving both Joule-heating related thermal runaway control and DC bias control until the quantum of conductance (12.9 kohm) is reached to warrant controlled breaking of the wire from the Au-Ag interface of the anode electrode. Local joule heating and electromigration controlled break junctions were characterized using SEM and I-V measurements, showing the short and gap readouts.