Gap Engineered Superconducting Multilayer Nanobridge Josephson Junctions

TL;DR

This paper presents a new multilayer nanobridge Josephson junction design using Nb/NbN and Nb/TiN stacks, enabling gap engineering and scalable superconducting electronics without oxide barriers.

Contribution

Introduces a multilayer 3D nanobridge Josephson junction platform with engineered superconducting gaps, avoiding traditional oxide barriers and enabling scalable superconducting circuits.

Findings

Successful fabrication of multilayer nanobridge Josephson junctions.

Integration into dc SQUIDs demonstrating reliable operation.

Platform enables oxide-free, scalable superconducting electronics.

Abstract

We report the realization of multilayer three-dimensional nanobridge Josephson junctions based on Nb/NbN and Nb/TiN superconducting stacks fabricated using electron-beam lithography and chlorine-based dry etching. In this architecture, a high-resistivity nitride layer defines the geometrical weak link, while the top Nb layer sets the overall critical temperature and film quality of the stack. This multilayer design enables engineering of the superconducting gap and proximity effects without relying on focused ion beam milling or oxide tunnel barriers. The devices are successfully integrated into dc SQUIDs, demonstrating reliable circuit-level operation. By combining material selectivity with three-dimensional geometry, this platform provides a scalable route toward oxide-free Josephson junctions suitable for superconducting electronics.