Optimization of Al/AlOx/Al-layer systems for Josephson junctions from a microstructure point of view

Fritz, S., Radtke, L., Schneider, R., Weides, M. and Gerthsen, D. (2019) Optimization of Al/AlOx/Al-layer systems for Josephson junctions from a microstructure point of view. Journal of Applied Physics, 125(16), 165301. (doi:10.1063/1.5089871)

Fritz, S., Radtke, L., Schneider, R., Weides, M. and Gerthsen, D. (2019) Optimization of Al/AlOx/Al-layer systems for Josephson junctions from a microstructure point of view. Journal of Applied Physics, 125(16), 165301. (doi:10.1063/1.5089871)

[img] Text
185030.pdf - Published Version
Restricted to Repository staff only until 22 April 2020.

2MB
[img]
Preview
Text
185030.pdf - Accepted Version

2MB

Abstract

Al/AlOx/Al-layer systems are frequently used for Josephson junction-based superconducting devices. Although much work has been devoted to the optimization of the superconducting properties of these devices, systematic studies on the influence of deposition conditions, combined with structural analyses on the nanoscale, are rare up to now. We have focused on the optimization of the structural properties of Al/AlOx/Al-layer systems deposited on Si(111) substrates with a particular focus on the thickness homogeneity of the AlOx-tunnel barrier. A standard high-vacuum electron-beam deposition system was used, and the effect of substrate pretreatment, different Al-deposition temperatures, and Al-deposition rates was studied. Transmission electron microscopy was applied to analyze the structural properties of the Al/AlOx/Al-layer systems to determine the thickness homogeneity of the AlOx layer, grain-size distribution in the Al layers, Al-grain boundary types, and the morphology of the Al/AlOx interface. We show that the structural properties of the lower Al layer are decisive for the structural quality of the whole Al/AlOx/Al-layer system. Optimum conditions yield an epitaxial Al(111) layer on a Si(111) substrate with an Al-layer thickness variation of only ±1.6 nm over more than 10 μm and large lateral grain sizes up to 1 μm. Thickness fluctuations of the AlOx-tunnel barrier are minimized on such an Al layer, which is essential for the homogeneity of the tunnel current. Systematic variation of the Al-deposition rate and deposition temperature allows one to develop an understanding of the growth mechanisms.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Weides, Professor Martin
Authors: Fritz, S., Radtke, L., Schneider, R., Weides, M., and Gerthsen, D.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:Journal of Applied Physics
Publisher:AIP Publishing
ISSN:0021-8979
ISSN (Online):1089-7550
Published Online:22 April 2019
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Journal of Applied Physics 125(16):165301
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

University Staff: Request a correction | Enlighten Editors: Update this record