Fabrication of natural-barrier ramp-edge Josephson junctions

We have studied the effect of process parameters on the natural-barrier ram p-edge Josephson junctions using YBa2Cu3Ox electrodes, in order to improve uniformity and reproducibility of junctions. The natural barrier is formed during an etching process and an annealing process. The junction properties are controlled by an annealing temperature and an annealing pressure. Also the junction characteristics depend on the ramp-edge angle. After ramp str ucturing, a bulge of the underelectrode is observed by AFM. The IcRn produc ts of the junctions with the bulge of the ramp surface reach 2 mV at 4.2 K. We speculate that the etching condition is a very important parameter in t he junction fabrication.