Fabrication of YBa/sub 2/Cu/sub 3/O/sub 7/ ramp-type junctions by interface treatments

We have investigated ramp-type junctions with barriers fabricated by interface treatments instead of epitaxially grown barrier layers. In our approach, YBa/sub 2/Cu/sub 3/O/sub 7/ ramps were treated with Ar ions in a Kaufmann-type source and subsequently annealed prior to the deposition of the top electrode. The I-V curves of the junctions as well as the power dependence of the Shapiro step height can be well described by the RSJ-model. At 77 K the critical current density is 10 kA/cm/sup 2/, and the critical voltage is about 30 /spl mu/V. The strong modulation of the critical current with external magnetic field indicates the formation of a homogeneous barrier layer at the interface. The temperature dependence of critical current and normal resistance suggests a metallic barrier as interface layer.