Superconducting transition in Nb nanowires fabricated using focused ion beam

TL;DR

This paper investigates how focused ion beam fabrication affects the superconducting properties of Nb nanowires, revealing a transition from Josephson-like to insulating behavior and suggesting a method to engineer ultra-narrow superconducting nanowires.

Contribution

It demonstrates the impact of FIB-induced Ga-impurity poisoning on Nb nanowires and proposes a way to create sub-10 nm superconducting phase-slip nanowires.

Findings

Suppression of superconductivity in 100 nm wide nanowires.

Observation of phase-slip activation below Tc.

Potential to engineer sub-10 nm superconducting nanowires.

Abstract

Making use of focused Ga-ion beam (FIB) fabrication technology, the evolution with device dimension of the low-temperature electrical properties of Nb nanowires has been examined in a regime where crossover from Josephson-like to insulating behaviour is evident. Resistance-temperature data for devices with a physical width of order 100 nm demonstrate suppression of superconductivity, leading to dissipative behaviour that is shown to be consistent with the activation of phase-slip below Tc. This study suggests that by exploiting the Ga-impurity poisoning introduced by the FIB into the periphery of the nanowire, a central superconducting phase-slip nanowire with sub-10 nm dimensions may be engineered within the core of the nanowire.