On the Switching Current and the Re-Trapping Current of Tungsten Nanowires Fabricated by Focussed Ion Beam (FIB) Technique

Abstract We report the superconducting properties of the tungsten (W) nanowires fabricated using focussed ion beam (FIB) technique having different wire widths of ∼120 nm and ∼290 nm. The transport properties of these wires were measured down to a temperature of 20 mK in a dilution refrigerator. We observed hysteretic current- voltage characteristics (IVCs) as a function of temperature, wherein the extend of hysteresis (difference between switching current and re-trapping current) is larger at lower temperature and diminishes near to the transition temperature. The temperature dependence of the switching current and re-trapping current were analysed using conventional models and found out to be of reasonable agreement with the models invoked. The re-trapping current agrees well with the thermal model incorporating phonon contribution in the heat dissipation process along with the electronic contribution. The equilibrium electron temperature calculated using the heat dissipation models at the critical current of the wires agrees well with respect to the transition temperature of the wire having a larger width, while for the wire of lower width, it is slightly elevated. Based on the analysis, it is believed that heat dissipation primarily because of Joule heating is the cause of the hysteretic current voltage characteristics of the nanowires.