Dresden 2020 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 16: Poster Session Superconductivity, Cryogenic Particle Detectors, Cryotechnique
TT 16.25: Poster
Monday, March 16, 2020, 15:00–19:00, P2/EG
Characterization of Nb/Al-AlOx/Nb Josephson tunnel junctions suited for SQUID applications — •Fabienne Bauer, Dominik Zehender, Felix Herrmann, Constantin Schuster, Christian Enss, and Sebastian Kempf — Kirchhoff-Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
Josephson tunnel junctions (JJs) are the basic element of many superconducting electronic devices such as qubits, Josephson voltage standards or superconducting quantum interference devices (SQUIDs). Since many recent applications strongly demand for circuits involving a large number of Josephson junctions, a reliable wafer-scale fabrication process yielding JJs with a reproducible and uniform high quality as well as a small parameter spread is required. To potentially readjust critical fabrication parameters, the quality of the fabricated JJs has to be continuously monitored.
In this contribution, we present our methods and approaches to characterize our home-made Nb/Al-AlOx/Nb junctions which are utilized for SQUID applications. Current-voltage characteristics are recorded to check for the scaling of junction parameters like the critical current Ic with respect to the junction area and to extract different figures of merit such as the ratio of subgap to normal state resistance Rsg/RN or the IcRN-product. To further check for the quality of the tunnel barrier, we measure the magnetic field dependence of Ic. In addition, we use unshunted SQUIDs to determine the intrinsic junction capacitance.