High-throughput nanogap formation is reported for simultaneous fabrication of integrated nanogap arrays. Ten series-connected nanogaps with butterfly and bottle shapes were integrated by using electromigration induced by a field emission current (“activation”). Initially, ten series-connected butterfly-shaped nickel (Ni) nanogaps were fabricated with electron-beam lithography and lift-off processes. Activation with a preset current of 300 nA reduced the separation of the gaps to <10 nm. Similar results for bottle-shaped nanogaps indicated that integration of nanogaps using activation is not dependent on nanogap shape. The activation method was also used for the mass production of 30 identical nanogaps. Overall, the distance between the Ni nanogap electrodes was completely controlled by activation.

Controlling the tunnel resistance of suspended Ni nanogaps using field-emission-induced electromigration J. Vac. Sci. Technol. B 33, 02B107 (2015); 10.1116/1.4904731Fabrication of planar-type Ni/vacuum/Ni tunnel junctions based on ferromagnetic nanogaps using field-emissioninduced electromigrationWe present a simple technique for simultaneous control of the electrical properties of multiple Ni nanogaps. This technique is based on electromigration induced by a field emission current and is called "activation." Simultaneous tuning of the tunnel resistance of multiple nanogaps was achieved by passing a Fowler-Nordheim (F-N) field emission current through an initial group of three Ni nanogaps connected in series. The Ni nanogaps, which had asymmetrical shapes with initial gap separations in the 80-110-nm range, were fabricated by electron-beam lithography and a lift-off process. By performing the activation procedure, the current-voltage properties of the series-connected nanogaps were varied simultaneously from "insulating" to "metallic" via "tunneling" properties by increasing the preset current of the activation procedure. We can also simultaneously control the tunnel resistances of the series-connected nanogaps, which range from a resistance of the order of 100 TX-100 kX, by increasing the preset current from 1 nA to 30 lA. This tendency is quite similar to that of individually activated nanogaps, and the tunnel resistance values of the simultaneously activated nanogaps were almost the same at each preset current. These results clearly imply that the electrical properties of the series-connected nanogaps can be controlled simultaneously via the activation procedure. V C 2015 AIP Publishing LLC.

Articles you may be interested inFabrication of planar-type Ni/vacuum/Ni tunnel junctions based on ferromagnetic nanogaps using field-emissioninduced electromigrationThe authors report on the ability to control the tunnel resistance of suspended Ni nanogaps by field-emission-induced electromigration. This method is called "activation." Suspended Ni nanogaps are ideal for investigating activation because the leakage currents flowing through the substrates are suppressed in these structures. The tips of suspended Ni nanogap electrodes are isolated from the SiO 2 substrates, so it is expected that the suspended Ni nanogaps act as isolated tunnel junctions during activation. After undergoing activation, the suspended Ni nanogaps clearly exhibited tunneling I-V properties. Furthermore, the authors were able to tune the tunnel resistance of the suspended Ni nanogaps using the activation method. When the applied voltage was swept, the device current switched between high-and low-resistance states. The results imply that activation is a viable method for modulating the electrical properties of suspended Ni nanogaps at the nanometer scale.

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