Berlin 2024 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 18: Superconductivity: Poster
TT 18.49: Poster
Monday, March 18, 2024, 15:00–18:00, Poster C
Challenges Of Cross-Type Nb/Al-AlOx/Nb Tunnel Junction Fabrication — •A. Stoll1, F. Bauer2,1, L. Münch1, D. Hengstler1, A. Ferring-Siebert1, N. Kahne1, D. Mazibrada1, A. Reifenberger1, A. Fleischmann1, S. Kempf2,3,1, and C. Enss1 — 1KIP, Heidelberg University — 2IMS, Karlsruhe Institute of Technology — 3IPE, Karlsruhe Institute of Technology
Superconducting Quantum Interference Devices (SQUIDs) are among the most sensitive wideband detectors for magnetic flux today. Based on the Josephson effect, they are able to convert small magnetic flux changes into a measurable voltage signal. For this study, microfabricated Josephson tunnel junctions (JJs) make up the basic elements of the SQUIDs.
Very often window-type JJs are used due to their reliable wafer-scale fabrication process. The JJ area in the window-type geometry is defined by openings in an insulating layer and is thus limited in its size by the alignment accuracy. To circumvent this, the cross-type geometry was introduced in which the JJ area is defined by the overlap area of two crossing stripes.
The transition to cross-type JJs is motivated by reducing the junction area as well as parasitic capacitances. This will in turn relax parasitic effects, e.g. LC-resonances, as well as improve the energy resolution є∝ √LC of dc-SQUIDs.
We present the characteristic properties, performance and noise spectra of different design variants of dc-SQUIDS based on cross-type JJs. These results showcase the potential of moving even closer to the quantum limit by utilising the cross-type geometry.
Keywords: Cross-type Josephson tunnel junctions; dc-SQUIDs