Tuning of Tunnel Resistance of Nanogaps by Field-Emission-Induced Electromigration Using Current Source Mode

Abstract

A newly investigated technique for the tuning of the tunnel resistance of nanogaps using electromigration method induced by a field emission current is presented to reduce the power consumption during the process. The method is called "activation" and is demonstrated with a current source. Planar-type initial nanogaps of Ni separated by 20-80 nm were defined on SiO2/Si substrates via electron-beam lithography and the lift-off process. Then, a bias current was applied to the initial nanogaps at room temperature, using a current source. The applied current was slowly ramped up until it reached the preset value. As a result, the process time of the current-source-based activation was 16 times shorter than activation using a voltage source. Furthermore, the tunnel resistance of the nanogaps was reduced from 100 T ohms to 70 M ohms by increasing preset current I(s) from 1 nA to 3.5 microA. Regarding the average power required for current-source-based activation, it can be successfully suppressed compared with that of voltage-source-based activation. These results imply that the current source directly and precisely tunes the field emission current passing through the nanogaps, and effectively causes the migration of atoms across the nanogaps, resulting in the successful control of the tunnel resistance of the nanogaps.

Tuning of resistance of nanogaps using field-emission-induced electromigration with feedback control scheme

“…In our previous work, the tunnel resistance of nanogaps can be controlled by only the magnitude of the field emission current during the activation [9][10][11]. Therefore, it is expected that one can tune the resistance of nanogaps more precisely, in which the gap is sufficiently narrowed even at the final stage of activation, with a feedback control scheme.…”

“…However, the nanogap electrodes fabricated by this method tend to exhibit high tunnel resistance [7,8]. We have already reported that the control of tunnel resistance of nanogap electrodes is performed by field-emission-induced electromigration, which is the so called "activation" [9][10][11]. The advantage of this method is that the tunnel resistance of nanogaps can be extensively tuned by only the magnitude of the field emission current during activation.…”

Conduction mechanism of single-electron transistors fabricated by field-emission-induced electromigration

“…We call this "activation" method. The activation method is based on moving the atoms induced by the Fowler-Nordheim (F-N) field emission current passing through the nanogaps between source and drain electrodes [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. In the activation procedures, it is expected that the moved atoms accumulate within the gaps and play the dual role of reducing the gap width and forming SETs islands [15][16][17][18].…”

Electrical properties of nanogap-based single-electron transistors fabricated by field-emission-induced electromigration

“…The activation method is based on moving the atoms induced by the Fowler-Nordheim (F-N) field emission current passing through the nanogaps between source and drain electrodes [6][7][8][9][10][11][12][13]. In the activation procedures, it is expected that the moved atoms accumulate within the gaps and play the dual role of reducing the gap width and forming the SETs islands [12,13].…”