Resistive switching effects in electromigrated Ni nanogaps

Recently, resistive switches have been constructed from nanogap electrodes. We have already reported a simple method for the fabrication of nanogaps with well-controlled tunnel resistance, which is called “activation”. Since the activation is considered to be the method of transferring atoms across the nanogap, it is expected that a resistive switching effect is caused in the nanogaps controlled by the activation method. In this study, we explore a resistive switching effect of Ni nanogaps using the activation. First, by applying the activation, the tunnel resistance of Ni nanogaps was sufficiently decreased with increasing the field emission current passing through the nanogaps. Then, during the subsequent voltage sweep, the characteristic electrical properties exhibited current increase and decrease, showing the typical set (higher conduction) and reset (lower conduction) processes, respectively. Actually, set/reset state can be controlled with applying pulse voltages, and the conduction states were successfully read out. In this method, the endurance was more than 100 cycles and the resistive ratio was obtained to be about 10³. The results suggest that resistive switching properties are successfully observed using nanogaps controlled with activation method.