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RESEARCH PRODUCT

Josephson junctions and SQUIDs based on artificial grain boundaries in Bi 2 Sr 2 Ca 2 Cu 3 O 10 -thin films

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ABSTRACT High quality thin films of Bi2 Sr Ca2 Cu3 0 with critical temperatures of 95 K were used to prepare grainboundary josephson junctions on commercial 36.8° SrTiOg-bicrystal substrates. IR-products of 50 pV at 77 Kand 0.7 mV at 4.2 K have been reached. For temperatures higher than 50 K the current-voltage curves of thejunctions can be well described by the resistively shunted junction (RSJ) model and show no hysteresis. Fromthe hysteretic behavior at low temperature we estimate a junction capacitance of 2ljiF/cm2. The Fraunhoferpattern of the critical current in an external applied field shows, that the junctions are inhomogeneous on a pm scale. The SQUID modulation of a 30 x 40 pm2 wide superconducting ioop containing two 10 pm wide junctions yields a flux-voltage transfer function of 2.7 pV/o at 78 K.Keywords: high-Ta superconducting thin film devices, grain boundary Josephson junctions, BiSr2 Ca Cu Oc 1 INTRODUCTION Most electronic device applications of high T superconductors (HTSC) are based on YBa2 Cu 07(YBCO)