Simultaneous fabrication of nanogaps using field-emission-induced electromigration

We present a simple and easy technique for the simultaneous control of electrical properties of multiple Ni nanogaps. This technique is based on electromigration induced by a field emission current, which is so-called “activation”. The tuning of tunnel resistance of nanogaps was simultaneously achieved by passing a Fowler-Nordheim (F-N) field emission current through three initial Ni nanogaps connected in series. The Ni nanogaps having an asymmetrical shape with an initial gap separation of 80-110 nm were fabricated by electron-beam (EB) lithography and lift-off process. By performing the activation, current-voltage properties of series-connected nanogaps were simultaneously varied from “insulating” to “metallic” through “tunneling” properties with increasing the preset current of the activation. Furthermore, we can simultaneously control the tunnel resistance of the series-connected nanogaps ranging from the order of 100 TΩ to 100 kΩ with increasing the preset current from 1 nA to 30 μA. This tendency is quite similar to that of individually activated nanogaps, and it should be noted that tunnel resistance of simultaneously activated nanogaps was almost the same at each preset current. These results clearly imply that the electrical properties of series-connected nanogaps can be simultaneously controlled by the activation procedure.