YBA2CU3O7-DELTA JOSEPHSON-JUNCTIONS ON DIRECTIONALLY ION-BEAM ETCHED MGO SUBSTRATES

Shallow, 1-40 nm deep steps were ion beam milled at 60-degrees angle o f incidence to the normal of the MgO substrate in order to form Joseph son junctions. Microbridges were patterned across the step boundary in films of YBa2Cu3O7-delta. They displayed critical current densities a nd critical current-normal resistance products that, on the whole, dec reased with increasing step height, leveling off at about 5 nm. Transm ission electron microscopy showed the presence of 45-degrees [001]-til t regions in the films close to the steps. Interferometers (dc-SQUIDs) showed magnetic field response at temperatures above 77 K and a noise level of about 1.5 x 10(-8) PHI0(2)/Hz at 10 Hz and 4.2 K.