HIGH-T(C)-BASED JOSEPHSON-JUNCTIONS AND SQUIDS BY MECHANICALLY INDUCED GROWTH DISORDER

We have developped a simple method for the reproducible production of high-T(c) based Josephson junctions and SQUIDs. By producing a very we ak deformation into the substrate surface by a diamond needle before d epostion of the thin high-T(c)-film, the film shows a growth disturban ce in the region of the deformation with quite interesting features, r esulting in a Josephson junction. The substrate deformation is charact erized by Atomic Force Microscopy and the film growth over the deforma tion is examined by Scanning Electron Microscopy. The junctions produc ed by this method show RSJ-like behaviour in their current-voltage cha racteristics and Shapiro-steps at all temperatures between 4.2 and 89K , when exposed to microwave power. The I(c)R(n)-products are variable in a wide range and can be very high for properly chosen film thicknes ses. SQUIDs produced by this method show voltage modulations due to dc -flux of up to 12muV peak to peak at 77K for low SQUID-performance par ameters beta << 1. For beta >> 1 the modulations are between 3 and 5mu V at 77K. Finally the noise in SQUIDs produced by this method is exami ned. It is shown that the noise power is in the region of that of step edge junctions.