# Direct-Write Ion Beam Irradiated Josephson Junctions

## TL;DR

This paper demonstrates the controlled fabrication of YBa2Cu3O7 Josephson junctions using focused helium ion beam irradiation, showing reproducible electrical properties and a transition from SNS to SIS behavior with increasing dose.

## Contribution

It introduces a method for precise, reproducible creation of Josephson junctions with tunable properties via ion beam irradiation, including large uniform arrays.

## Key findings

- Junctions exhibit SNS behavior at low doses.
- Transition to SIS behavior occurs at higher doses.
- Arrays of 20 junctions show high uniformity.

## Abstract

We highlight the reproducibility and level of control over the electrical properties of YBa$_2$Cu$_3$O$_7$ Josephson junctions fabricated with irradiation from a focused helium ion beam. Specifically, we show the results of electrical transport properties for several junctions fabricated using a large range of irradiation doses. At the lower end of this range, junctions exhibit superconductor-normal metal-superconductor (SNS) Josephson junction properties. However, as dose increases there is a transition to electrical characteristics consistent with superconductor-insulator-superconductor (SIS) junctions. To investigate the uniformity of large numbers of helium ion Josephson junctions we fabricate arrays of both SNS and SIS Josephson junctions containing 20 connected in series. Electrical transport properties for these arrays reveal very uniform junctions with no appreciable spread in critical current or resistance.