Step-edge Josephson junctions and their use in HTS single-layer gradiometers

We describe a reproducible technology for fabricating YBa2Cu3O7 step-edge J osephson junctions on SrTiO3 substrates, We report on the electrical charac teristics of the junctions at 77 K and the dependence on the ratio of film thickness to step height. Single-layer gradiometers incorporating step-edge junction de SQUIDs have been fabricated. We compare the performance of ide ntical SQUID gradiometers based on our step-edge junctions and on 24 degree s degrees SrTiO3 bicrystal junctions. Gradiometric SQUIDs (G-SQUIDs) incorp orating step-edges have also been fabricated. We measured the effective are a of several G-SQUIDs to be in the range of 1-2 mum(2) approximately two or ders of magnitude lower than for conventional SQUIDs of similar inductance. We demonstrate that when incorporated into a gradiometer the G-SQUID leads to an improved performance in an unshielded environment.