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

A new fabrication method for superconductor-normal metal-superconductor jun ctions employing focused ion beam patterning of a superconductor-normal met al bilayer has been used to make series junction arrays. We investigated th eir current-voltage (I-V) characteristic and examined their response to mic rowaves at 4.2 K. Multiple integer Shapiro steps were observed in the I-V r esponse of an array to microwaves. In addition, we found that the propertie s of each junction in a double-junction series array did not change in the junction spacing range studied (0.2-8 mu m). Modelling the I-V characterist ic of large arrays showed the junction variation of the critical current wa s 20%.