IMPROVED PROCESS FOR HIGH-T(C) SUPERCONDUCTING STEP-EDGE JUNCTIONS

We have developed a process for the fabrication of YBaCuO high-T(c) ju nctions based on the step-edge weak-link concept. The process emphasiz es the creation of sharp and straight step edges on a substrate, and t he restoration of oxygen content for superconducting materials at the step edges. A diamond-like carbon film is used as an ion milling mask for the creation of steps on substrates such as LaAlO3 and SrTiO3. Roo m-temperature plasma oxidation is shown to be effective in restoring T (c) from processing related degradation for grains residing at the ste p edge. Using this process, dc SQUIDs were fabricated with 77 K electr ical performances matching, and in certain cases exceeding, similar SQ UIDs made using bicrystal-based tilt-boundary weak-link junctions.