Realization and properties of ramp-type YBa2Cu3O7-delta/Au/Nb junctions

All-thin-film ramp type Josephson junctions between YBa2Cu3O7-delta and Nb have been fabricated. This procedure allows connections between high-T-c an d low-T-c superconductors at different crystal sides of the high-T-c superc onductor on one chip, which is of great interest for novel phase devices. A thin Au layer is incorporated as a chemical barrier to avoid oxygen transf er from the YBa2Cu3O7-delta to the Nb. Critical current densities up to 600 A/cm(2) are obtained at T = 4.2 K, with typical R(n)A values of similar to 0.8 mu Omega cm(2). The variation of the magnetic field dependence of the c ritical current with the angle between the junction barrier and the YBa2Cu3 O7-delta crystal axes is explained by considering a predominant d(x2-y2) or der parameter symmetry of the YBa2Cu3O7-delta The successful fabrication of these junctions allows the implementation of novel superconducting electro nics, such as complementary Josephson circuitry or proposed qubit concepts, using the unconventional order parameter symmetry of the high-T-c supercon ductor. (C) 2001 Elsevier Science B.V. All rights reserved.