SINGLE AND STACKED JOSEPHSON-JUNCTIONS BASED ON C-AXIS YBCO PBCO MULTILAYERS/

Using Whole Wafer superconducting device technology we have fabricated vertically stacked sandwich junctions with c-axis oriented YBCO/PBCO/ YBCO trilayers and double barrier junctions. The resulting devices exh ibit supercurrents through PBCO thicknesses of up to 130 nm at 4.2K. W e have observed RSJ-like I-V curves, Shapiro steps and almost Fraunhof er-like dependence of the critical current as a function of magnetic f ield. The scaling behavior of devices fabricated on perovskite (SrTiO3 and LaAlO3) and MgO substrates differ. The results indicate a certain uniformity for the barriers on the scale of the size of the junction. We propose different mechanisms for supercurrent and quasiparticle tr ansport through the PBCO barrier for the two substrate types.