All-NbN DC SQUIDs with nanobridges fabricated by burn-in technique

Using an epitaxial NbN films and ''burn-in'' techniques, the authors fabricated all-NbN DC SQUIDs with nanobridges. NbN/MgO/NbN tri-layers first exhibit very high resistance above 1MΩ at 4.2 Km and there is no supercurrent. The DC SQUIDs with the desired L/sub s/I/sub o//PHI/sub o/ ratio was produced by ''burn-in'' technique in liquid He bath. The junction capacitance is about 0.01 pF/μm/sup 2/, and the maximum voltage modulation is about 80μV for an uncoupled SQUIDs with an inductance of about 0.2 nH. The maximum value of transfer function absolute value of ∂V/∂ PHI/sub o/ is about 2 mV/PHI/sub o/. These SQUIDs show no change after repeated thermal cycling and storage over a year