Investigation of NanoSQUIDs Fabricated with a Range of Focused Ion Beam Sources

E Polychroniou,J Chen,G Long,D Cox,T Godfrey,E Romans,J Gallop,L Hao

doi:10.1088/1742-6596/1559/1/012015

Abstract

SQUIDs (Superconducting Quantum Interference Devices) are macroscopic quantum devices capable of detecting and measuring a wide variety of physical parameters with unprecedented sensitivity. SQUIDs based on nanobridge weak links have shown increasing promise for quantum information and quantum sensing applications such as single spin detection. Focussed ion beam etched nanobridges have properties which can enhance nanoSQUID device performance but are often limited in terms of their non-hysteretic operating temperature range. Here we describe measurements of FIB-milled nanobridges, as single weak links or in nanoSQUIDs, made using either Ga, Xe or Ne ion beam sources. Their properties as a function of temperature, bias current, magnetic field and microwave power are measured and modelled according to a range of superconductivity models, as a means for improved understanding of the associated nanobridge parameters. We further propose techniques to extend the non-hysteretic operating temperature range of the devices.

Highlights

As superconducting devices extend their regimes of application to lower temperatures, as demanded by quantum technologies, and to smaller length scales, as demanded by nanoscience, the workhorse trilayer Josephson junctions [1,2,3] are increasingly challenged
In this paper we present results for nanobridge junctions fabricated in single layer Nb films using a focused ion beam (FIB) to etch the film down to the nanoscale
We present results on junctions and SQUID devices fabricated with three different ion beam sources (Ga, Xe and Ne), demonstrating their resistance as a function of temperature (R-T), current-voltage characteristics (I-V) and the observation of microwave induced Shapiro step characteristics

Summary

Introduction

As superconducting devices extend their regimes of application to lower temperatures, as demanded by quantum technologies, and to smaller length scales, as demanded by nanoscience, the workhorse trilayer Josephson junctions [1,2,3] are increasingly challenged. Other superconducting electronic technologies for fabricating Josephson junctions may have advantages in these areas but may suffer from different limitations. In this paper we present results for nanobridge junctions fabricated in single layer Nb films using a focused ion beam (FIB) to etch the film down to the nanoscale. We present results on junctions and SQUID devices fabricated with three different ion beam sources (Ga, Xe and Ne), demonstrating their resistance as a function of temperature (R-T), current-voltage characteristics (I-V) and the observation of microwave induced Shapiro step characteristics.

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Results

Conclusion