An argon ion beam milling process for native AlOx layers enabling coherent superconducting contacts

Grünhaupt, L. et al. (2017) An argon ion beam milling process for native AlOx layers enabling coherent superconducting contacts. Applied Physics Letters, 111(7), 072601. (doi: 10.1063/1.4990491)

Abstract

We present an argon ion beam milling process to remove the native oxide layer forming on aluminum thin films due to their exposure to atmosphere in between lithographic steps. Our cleaning process is readily integrable with conventional fabrication of Josephson junction quantum circuits. From measurements of the internal quality factors of superconducting microwave resonators with and without contacts, we place an upper bound on the residual resistance of an ion beam milled contact of 50 mΩ μm2 at a frequency of 4.5 GHz. Resonators for which only 6% of the total foot-print was exposed to the ion beam milling, in areas of low electric and high magnetic fields, showed quality factors above 106 in the single photon regime, and no degradation compared to single layer samples. We believe these results will enable the development of increasingly complex superconducting circuits for quantum information processing.

• Item Type: Articles
• Additional Information: Funding was provided by the Alexander von Humboldt foundation in the framework of a Sofja Kovalevskaja award endowed by the German Federal Ministry of Education and Research. I.M.P. and M.W. acknowledge partial financial support from the KIT Young Investigator Network (YIN). M.W. acknowledges funding by the European Research Council (CoG 648011). D.G. acknowledges support from the Karlsruhe House of Young Scientists (KHYS). D.G. and A.U. acknowledge partial support from the Russian Federation Ministry of Education and Science (NUST MISIS Contract No. K2-2016-063).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Weides, Professor Martin
• Authors: Grünhaupt, L., von Lüpke, U., Gusenkova, D., Skacel, S. T., Maleeva, N., Schlör, S., Bilmes, A., Rotzinger, H., Ustinov, A. V., Weides, M., and Pop, I. M.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Journal Name: Applied Physics Letters
• Publisher: AIP Publishing
• ISSN: 0003-6951
• ISSN (Online): 1077-3118
• Published Online: 16 August 2017
• Copyright Holders: Copyright © 2017 AIP Publishing
• First Published: First published in Applied Physics Letters 111(7): 072601
• Publisher Policy: Reproduced in accordance with the publisher copyright policy