Interface-modified YBCO ramp-edge Josephson junctions by deionized water

We have investigated YBa 2 Cu 3 O 7-x (YBCO) ramp-edge Josephson junctions by reacting the ramp-edge interface with deionized water. YBa 2 Cu 3 O 7-x /PrBa 2 Cu 3 O x (YBCO/PBCO) films were deposited on SrTiO 3 (100) by on-axis KrF laser deposition. After patterning the bottom YBCO/PBCO layer, the ramp edge was cleaned by Br-in-ethanol and then reacted with deionized water. The top YBCO/PBCO layer was deposited and patterned by photolithography and ion milling. We measured the current-voltage (I-V) characteristics, magnetic field modulation of the critical current and microwave response at 10 GHz. The 20-minute water-immersed junction showed resistively shunted junction (RSJ)-type I-V characteristics, while others exhibited flux-flow behaviour. The average values of I c , R n and I c R n of these RSJ-type junctions were 4 mA, 0.1 Ω and 400 μV, respectively, and Shapiro steps were fitted well by the microwave characteristic parameter Ω (= hf/2eI c R n ) = 0.18.

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