Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 49: Superconductivity: Superconducting Electronics I

TT 49.12: Talk

Wednesday, March 14, 2018, 12:45–13:00, H 2053

An argon ion beam milling process for native AlO_x layers enabling coherent superconducting contacts — Lukas Grünhaupt¹, Uwe von Lüpke¹, •Daria Gusenkova¹, Sebastian T. Skacel¹, Nataliya Maleeva¹, Steffen Schlör¹, Alexander Bilmes¹, Hannes Rotzinger¹, Alexey V Ustinov^1,2, Martin Weides^1,3, and Ioan M. Pop¹ — ¹Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany — ²Russian Quantum Center, National University of Science and Technology MISIS, 119049 Moscow, Russia — ³Physikalisches Institut, Johannes Gutenberg University Mainz, 55128 Mainz, Germany

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 [1]. Our cleaning process enables integration of complex superconducting quantum circuits without compromising their coherence properties. From measurements of the internal quality factors of superconducting microwave resonators, we place an upper bound on the residual resistance of an ion beam milled contact of 50 Ω ·µm² at a frequency of 4.5 GHz. Resonators for which only 6% of the total foot-print in areas of high magnetic field was exposed to the ion beam milling showed quality factors above 10⁶ in the single photon regime, and no degradation compared to single layer samples.

[1] L. Grünhaupt et al., Applied Physics Letters, 111, 072601 (2017).