Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 49: Poster Session: Superconductivity

TT 49.34: Poster

Mittwoch, 3. April 2019, 15:00–18:30, Poster D

YBCO nanoSQUIDs on bi-crystal MgO — •Jianxin Lin, Benedikt Mueller, Julian Linek, Max Karrer, Reinhold Kleiner, and Dieter Koelle — Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universität Tübingen, Germany

We report on the fabrication and characterization of nanopatterned YBa2Cu3O7 (YBCO) dc SQUIDs based on grain boundary Josephson junctions (GBJJs). The nanoSQUIDs are fabricated by epitaxial growth of YBCO films via pulsed laser deposition on MgO bicrystal substrates with 24* misorientation angle. Nanopatterning is performed by Ga focused ion beam (FIB) milling. Due to its much lower dielectric permittivity , as compared to SrTiO3 (STO), the use of MgO substrates avoids a significant stray capacitance of the GBJJs and hence provides nonhysteretic current-voltage characteristics (IVCs) at low temperature (4.2 K), even without a resistively shunting Au layer on top of YBCO. Hence, our approach of using MgO instead of STO offers the potential of achieving a much larger characteristic voltage and therfore a significantly improved noise performance of unshunted YBCO nanoSQUIDs.

On the other hand, the role of Au on top of YBCO as a protection layer during FIB milling has not been clarified yet. Here, we present experimental results on electric trans*port and noise properties of our YBCO nanoSQUDs on MgO that have been fabricated with different Au shunt layer thicknesses or even with*out Au on top of YBCO, and we discuss promising routes to further improve the performance of such YBCO nanoSQUDs.