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

We report a simple and easy method for the control of electrical characteristics of planar-type nanogap-based single-electron transistors (SETs) using field-emission-induced electromigration, which is so-called “activation”. The advantages of this method are as follows: (1) the fabrication of SETs is achieved by only passing a field emission current through a nanogap and (2) the charging energy of SETs can be controlled by the field emission current through a nanogap. When the activation with the preset current of 500 nA was applied to the nanogaps having initial gap separation of 48 nm, current-voltage characteristics of the activated nanogaps displayed the suppression of electrical current at low-bias voltages known as Coulomb blockade at room temperature. In addition, strong Coulomb staircases were clearly obtained, and the quasi-periodic current oscillations were also observed at room temperature. These results indicate that higher charging energy associated with a smaller Ni island structure within the multiple islands causes a bottleneck mechanism in conduction, improving the Coulomb staircase structures. Moreover, we successively performed the activation using the preset current Is of 500 nA to the nanogap with initial gap separation of 27 nm. Coulomb blockade voltage was clearly modulated by the gate voltage periodically at 16 K, resulting in the formation of single island in the SETs fabricated by the activation. These results imply that activation procedure allows us to simply and easily control electrical characteristics of planar-type nanogap-based SETs.