Fabrication of biepitaxial YBCO Josephson junctions on different substrates

Biepitaxial Josephson junctions were fabricated on MgO and SrTiO/sub 3/ (STO) substrates. Electrical characteristics such as the critical current densities J/sub c/, contact resistivities /spl rho//sub n/ and I/sub c/R/sub n/-products on both substrates are investigated. Junctions on MgO substrates are stable against thermal cycling in contrast to many junctions on STO substrates. The obtained current-voltage characteristics and Shapiro step oscillations are in agreement with the RSJ-model. The resistive transitions are strongly broadened. DC-SQUIDs patterned on both substrates show modulations dV/d/spl Phi/ at 77 K. At 55 K the energy resolution /spl epsi/ in the range of white noise lies within a factor of two of the theoretical limit.<
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