Fabrication of YBaCuO/nonsuperconductive-YBaCuO/YBaCuO co-planar Josephson junction by focused ion beam

A thin film of YBa/sub 2/Cu/sub 3/O/sub 7/(-/spl delta/) grown on an MgO substrate damaged by a focused ion beam loses superconductivity due to abnormal growth. We have fabricated a YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// co-planar Josephson junction whose coupling region is nonsuperconductive YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// grown on an MgO substrate damaged locally by focused ion beam scanning. The I-V characteristic of the junction behaves like a flux flow type. At temperatures from 4.2 K to 60 K, Shapiro steps were observed for the junctions in which the length of the coupling region was from 0.2 /spl mu/m to 1 /spl mu/m. The highest I/sub c/R/sub n/ product of the junction was 5.0 mV. The critical current density decreased exponentially with the junction length. It is considered that nonsuperconductive YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// grown on the damaged substrate works as a normal layer in an S-N-S junction. Also the junction responded to the magnetic field and behaved like an asymmetric dc-SQUID.<
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