Characteristics of intrinsic tunnel junctions on Bi-2223 thin films

We have successfully fabricated a small-sized thin stack with a small number of intrinsic junctions on (Bi,Pb)₂Sr₂Ca₂Cu₃O_10+x thin films. Mesa structures with the junctions are fabricated on the surface of high-quality films prepared by rf-sputtering and subsequent heat treatment. I–V characteristics along the c-axis for the thinnest stack show a 6-branch structure which corresponds to six tunnel junction arrays and the edge structure which represents the superconductive gap. The estimated superconductive gap values strongly depend on the number of junctions in the fabricated stack. For the thin stacks with 6-junctions, their gap values are about 65 mV at 4.2 K, which is two or three times as large as those previously reported for intrinsic junctions.