Characteristics of high performance YBa2Cu3O7 step-edge junctions

Step-edge Josephson junctions are engineered grain boundary junctions fabricated using standard lithographic and film deposition techniques. We report a systematic study of 180 YBa₂Cu₃O₇ step-edge junctions and identify a fabrication technique which results in a 90% yield of working junctions with critical current spreads from 30% to 50% (1σ/I_c-ave)over the entire substrate. Technically useful critical current values at 65 K can be obtained by adjusting YBa₂Cu₃O₇ film thickness. I_cRn values, approximately independent of film thickness, are ∼1 mV at 4.2 K and ∼0.1 mV at 65 K. Most junctions exhibit ideal electrical behavior in accordance with the RSJ model.