Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session

TT 33.41: Poster

Mittwoch, 28. März 2012, 15:00–19:00, Poster B

YBa₂Cu₃O₇ nanoSQUIDs for detection of small spin systems — •Tobias Schwarz¹, Joachim Nagel¹, Roman Wölbing¹, Matthias Kemmler¹, Siegfried Menzel², Reinhold Kleiner¹, and Dieter Koelle¹ — ¹Physikalisches Institut - Experimentalphysik II and Center for Collective Quantum Phenomena in LISA⁺, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany — ²Leibniz-Institut für Festkörper- und Werkstoffforschung (IFW) Dresden, D-01171 Dresden, Germany

We report on the fabrication and characterization of nanopatterned YBa₂Cu₃O₇ (YBCO) SQUIDs with grain boundary junctions (GBJs) for the investigation of small spin systems at 4 K and below. We use photolithography and Ar ion milling to prepattern bridges (several µm wide) in a YBCO/Au (50 nm/60 nm) bilayer across the grain boundary of a SrTiO₃ bicrystal substrate. Subsequently the final SQUID geometry with junction widths down to 80 nm is patterned by focused ion beam (FIB) milling, without significant reduction of critical current density (j_c>10⁵ A/cm² at 4.2 K) [1]. The Au layer serves as a shunt resistor to provide overdamped GBJs and protects the YBCO during the FIB process. We obtained a flux noise down to S_Φ^1/2≈ 600 nΦ ₀/Hz^1/2, corresponding to an estimated spin sensitivity S_µ^1/2≈ 65 µ_B/Hz^1/2
J. Nagel et al., Supercond. Sci. Technol. 24, 015015 (2011).