Interface-engineered junctions with YbBaCuO as the counter-electrode

The electric properties of interface-engineered junctions with YbBa/sub 2/Cu/sub 3/O/sub 7/ as the counter-electrode were investigated. The junctions exhibited excellent Josephson characteristics with the critical current density (J/sub c/) ranging from 10/sup 2/ A/cm/sup 2/ to more than 10/sup 6/ A/cm/sup 2/, and the normal resistance (R/sub n/) ranging from 10/sup – 6/ (omega)cm/sup 2/ to 10/sup -9/ (omega)cm/sup 2/. The R/sub n/ values varied approximately in accordance with J/sub c//sup -p/, where p was close to 0.25 for low-J/sub c/ junctions and increased gradually up to 0.75 for high-J/sub c/ junctions. The junctions with R/sub n/ exceeding 10/sup -7/ (omega)cm/sup 2/ exhibited dI/dV profiles peculiar to tunneling processes via localized states. The dI/dV profiles of the junctions with lower R/sub n/ were characterized by reproducible fine structures below 15 mV, probably due to multiple Andreev reflections. These results indicate that the crossover from the tunneling regime to metallic weak-links takes place in these junctions depending on the process conditions.