Investigation of the microstructure of ramp-type YBa2Cu3O7-δstructures

We studied the morphology of ramps in YBa2Cu3O7-δ films and, subsequently, the barrier layer. The ramps have been fabricated by Ar ion beam milling using standard photoresist masks. SEM and AFM showed the formation of tracks along the slope of the ramp, originating from the irregular shape of the edge of the photoresist mask. A proposed modified reflowed resist and pre-annealing process show a significantly smoother ramp surface, important for the fabrication of reproducible Josephson junctions.