Fabrication of YBaCuO junctions by the irradiation of focused ionbeam.

We have fabricated Josephson junctions in YBa2Cu3 O7-δ (YBaCuO) thin films by the irradiation of focused ion beam (FIB). We used Be2+ ions with the energy of 200 keV. When the fluence of Be2+ ions was 1.2×1016 ions/cm2, the I-V characteristics of the junctions at 4.2 K showed RSJ-like characteristics with the excess current. The IcRn product of the junctions was 1.1 mV at 6.3 K. Shapiro steps up to 20th step could be observed by the irradiation of 8.47 GHz microwave at 6.3 K. The magnetic modulation curve of the junction at 4.2 K was similar to the Fraunhofer pattern. These characteristics remained unaltered after preservation in a desiccator for 6 month