New techniques for fabricating step-edge junctions for high-T/sub c/ SQUIDs on MgO substrates

The authors describe two methods used to produce step-edge junctions on MgO substrates suitable for superconducting quantum interference devices (SQUIDs). In both processes a titanium mask has been used to produce a straight, well-defined step which assists in minimizing the occurrence of multiple junctions. They describe two ion-milling processes which produce differently connected step-edge junctions as indicated by scanning electron microscope (SEM) micrographs, and I-V and I/sub C/-B characteristics. Predictable relationships between the ratio of the film thickness to step height and the junction critical-current density are demonstrated; these enable the creation of step-edge junctions with appropriate values of I/sub C/ for particular SQUID designs.<
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