Overdamped Nb/Al-AlOx/Nb Josephson junctions

We report the fabrication and characterization of overdamped Nb/Al-AlO x/Nb superconductor-insulator-superconductor Josephson junction whose fabrication process derives from that of the well-known hysteretic junctions. These junctions are an intermediate state between the superconductor-normal metal-superconductor and the superconductor-insulator-superconductor Josephson junctions. Stable and reproducible nonhysteretic current-voltage characteristics are obtained with a proper choice of the fabrication parameters. We have measured critical current densities JC from 103 up to 2 × 104 A/cm 2, with characteristic voltages from 80 to nearly 450 ?V. The junctions are stable against time and repeated thermal cycling.