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TT: Fachverband Tiefe Temperaturen

TT 18: Superconductivity: Poster

TT 18.32: Poster

Montag, 18. März 2024, 15:00–18:00, Poster C

YBa₂Cu₃O₇ constriction-type Josephson junctions with integrated shunt resistors fabricated by focused-helium-ion-beam irradiation. — •Christoph Schmid¹, Moritz Meichsner¹, Dominik Hanisch², Max Pröpper², Meinhard Schilling², Edward Goldobin¹, Dieter Koelle¹, and Reinhold Kleiner¹ — ¹Physikalisches Institut, Center for Quantum Science and LISA⁺, Universität Tübingen — ²Institut für Elektrische Messtechnik und Grundlagen der Elektrotechnik, Technische Universität Braunschweig

We report on the investigation of YBa₂Cu₃O₇ (YBCO) Josephson junctions (JJs) fabricated by irradiation with a focused helium ion beam (He-FIB). With this method one can locally modify YBCO thin films, to write insulating or normal conducting regions, including Josephson barriers, depending on the He-FIB irradiation dose D. We investigated the electric properties of YBCO areas with typical lateral size of 30× 2000 nm², irradiated with D∼ 40 ions/nm². Such a dose preserves the YBCO crystal structure but supresses the critical temperature T_c completely. Thus, such areas can be used as shunt resistors with dose-dependent resistivity and ohmic I−V characteristics (IVCs). Moreover, we created constriction-type JJs (cJJs) between resistive areas. By constricting the cJJ width down to 6 nm, we observe resistively-shunted-junction (RSJ) like IVCs with small excess currents and characteristic voltages of 3 – 60 mV, making such JJs interesting for high-frequency applications. Our fabrication method opens a way to fabricate nano-circuits with integrated nm-sized cJJs and resistors/resistive areas during a single He-FIB irradiation process.

Keywords: Constriction Josephson junction; YBCO; He FIB