FABRICATION OF BIEPITAXIAL YBCO JOSEPHSON-JUNCTIONS ON DIFFERENT SUBSTRATES

Biepitaxial Josephson Junctions were fabricated on MgO and SrTiO3 (STO ) substrates. Electrical characteristics such;Is the critical current densities J(c), contact resistivities rho(n) and I(c)R(n)-products on both substrates are investigated. Junctions on MgO substrates are stab le against thermal cycling in contrast to many junctions on STO substr ates, The obtained current-voltage characteristics and Shapiro step os cillations are in agreement with the RSJ-model. The resistive transiti ons are strongly broadened. DC-SQUIDs patterned on both substrates sho w modulations dV/d Phi at 77 K. At 55 K the energy resolution epsilon in the range of white noise lies within a factor of two of the theoret ical limit.