Key components for the fabrication of YBa2Cu3O7-δ flip-chip SQUID magnetometers and current sensors

We have prepared single layer washer-type de superconducting quantum interference devices (SQUIDs), multilayer flux transformers and input coils as key components for flip-chip SQUID magnetometers and current sensors. The do SQUIDs are prepared on a SrTiO3 bicrystal substrate with a misorientation angle of 30 degrees. The maximum peak-to-peak flux modulated voltage amounts to typically 40-60 mu V for a SQUID inductance of 80 pH. YBa2Cu3O7-delta flux transformers and input coils are prepared on a SrTiO3 single crystal polished on both sides with dimensions 10 mm x 10 mm x 1 mm. The preparation process of these structures involves the deposition of YBa2Cu3O7-delta and SrTiO3 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 Phi(0)(-1) whereas current sensors show a sensitivity equal to 2.6 mu A Phi(0)(-1). The best value for the magnetic field resolution is 20 fT Hz(-1/2) in the white noise region and 100 fT Hz(-1/2) at 1 Hz with a 1/f corner at 10 Hz. Current resolution values are typically 40 pA Hz(-1/2) in the white noise region.