Key components for the fabrication of flip-chip SQUID magnetometers and current sensors

We have prepared single layer washer-type dc superconducting quantum interference devices (SQUIDs), multilayer flux transformers and input coils as key components for flip-chip SQUID magnetometers and current sensors. The dc SQUIDs are prepared on a bicrystal substrate with a misorientation angle of . The maximum peak-to-peak flux modulated voltage amounts to typically for a SQUID inductance of 80 pH. flux transformers and input coils are prepared on a single crystal polished on both sides with dimensions mm. The preparation process of these structures involves the deposition of and layers by pulsed laser ablation and pattern definition by dry etching. The flip-chip magnetometers with 80 pH SQUIDs provide a field sensitivity equal to 2.6 nT whereas current sensors show a sensitivity equal to . The best value for the magnetic field resolution is 20 fT in the white noise region and 100 fT at 1 Hz with a corner at 10 Hz. Current resolution values are typically 40 pA in the white noise region.