Fabrication of YBa2Cu3O7 ramp-type junctions by interface treatments

We have investigated ramp-type junctions with barriers fabricated by interf ace treatments instead of epitaxially grown barrier layers. In our approach ? YBa2Cu3O7 ramps were treated with Ar ions in a Kaufmann-type source and s ubsequently 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 77K the critical current density is 10 kA/cm(2), and the critical voltage is about 30 mu V. The str ong modulation of the critical current with external magnetic field indicat es the formation of a homogeneous barrier layer at the interface. The tempe rature dependence of critical current and normal resistance suggests a meta llic barrier as interface layer.