Fabrication of Josephson superconductor-normal metal-superconductor series arrays using a focused ion beam

A new fabrication method for superconductor-normal metal-superconductor junctions employing focused ion beam patterning of a superconductor-normal metal bilayer has been used to make series junction arrays. We investigated their current-voltage (I-V) characteristic and examined their response to microwaves at 4.2 K. Multiple integer Shapiro steps were observed in the I-V response of an array to microwaves. In addition, we found that the properties of each junction in a double-junction series array did not change in the junction spacing range studied (0.2-8 μm). Modelling the I-V characteristic of large arrays showed the junction variation of the critical current was 20%. (author)