FABRICATION OF HIGH-QUALITY NB/AL/ALOX/NB STACKED JOSEPHSON-JUNCTIONS

We have fabricated stacked Josephson junctions from a double trilayer structure deposited sequentially with the intermediate Nb layer slightly thicker than lambda(L). The lower electrode geometry was patterned by a sequence of Reactive Ion Etching and sputter-etching operations, while the junctions were defined by anodic oxidation of the top and the intermediate electrodes. We measured from the I-V characteristic the quasiparticle losses, finding V(m) congruent-to 65 mV. Moreover we found that the critical currents in the two junctions of each stack are similar within less than ten percent and the magnetic field patterns are very regular.