Atomic layer deposition (ALD) provides a promising approach for deposition of ultrathin low-defect-density tunnel barriers, and it has been implemented in a high-vacuum magnetron sputtering system for in situ deposition of ALD-Al2O3 tunnel barriers in superconductor-insulator-superconductor (SIS) Josephson junctions. A smooth ALD-Al2O3 barrier layer was grown on a Al-wetted Nb bottom electrode and was followed with a top Nb electrode growth using sputtering. Preliminary low temperature measurements of current-voltage characteristics (IVC) of the Josephson junctions made from these trilayers confirmed the integrity of the ALD-Al2O3 barrier layer. However, the IcRN product of the junctions is much smaller than the value expected from the Ambegaokar-Baratoff formula suggesting a significant pair-breaking mechanism at the interfaces.
@article{arxiv.1309.4410,
title = {Fabrication of Nb/Al2O3/Nb Josephson Junctions using in situ Magnetron Sputtering and Atomic Layer Deposition},
author = {Rongtao Lu and Alan J. Elliot and Logan Wille and Bo Mao and Siyuan Han and Judy Z. Wu and John Talvacchio and Heidi M. Schulze and Rupert M. Lewis and Daniel J. Ewing and H. F. Yu and G. M. Xue and S. P. Zhao},
journal= {arXiv preprint arXiv:1309.4410},
year = {2013}
}