SNS-DC-SQUIDs and flux transformers for integrated magnetometers in flip-chip technique

YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta///Ag/YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// Josephson-junctions across steps in MgO substrates were used to fabricate SNS-DC-SQUIDs in the step-and-gap geometry. The necessary break of the YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//-film at the step was confirmed by transmission electron microscopy investigations. The removal of the Ag-layer eliminates the shunt resistance on top of the HTSC which increases the normal resistance R/sub N/ by more than two orders of magnitude with only a slight reduction in I/sub C/. The junctions can be described by the SINS-formalism, which allows high I/sub C/R/sub N/-products with large values of the normal resistances R/sub N/. For thin-film flux transformer epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta///SrTiO/sub 3//YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// trilayers were grown using a co-sputter process. Test coils exhibited a current density in excess of 8/spl times/10/sup 5/ A/cm/sup 2/ and insulation resistivities of 10/sup 8/ /spl Omega/cm at 77 K. By coupling the flux transformers to SQUIDs using a flip-chip technology the magnetic field response were increased by a factor of 9.<
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