Simultaneous tuning of tunnel resistance of integrated nanogaps by field-emission-induced electromigration

We report a simple and easy method for the simultaneous control of electrical properties of multiple Ni nanogaps. This method is based on electromigration induced by a field emission current, which is the 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 the 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, the tunnel resistance of simultaneously activated nanogaps decreased from the order of 100 TΩ to 100 kΩ with increasing the preset current from 1 nA to 30 μA. Scanning electron microscopy (SEM) images of the nanogaps after performing the activation with the final preset current I_s of 30 μA clearly indicated that the separation of the gaps reduces to less than 10 nm after the activation. These results clearly imply that the electrical properties of series-connected nanogaps can be simultaneously tuned by the activation procedure.