Characteristics of Intrinsic Josephson Junctions in a Thin Stack on Bi-2223 Thin Films

Abstract

We have successfully fabricated a small thin stack with a small number of intrinsic junctions on (Bi, Pb)₂Sr₂Ca₂Cu₃O_10+xthin films. Mesa structures with the junctions are fabricated on the surface of high-quality films prepared by rf-sputtering and subsequent heat treatment. Current-voltage (I–V) responses along thec-axis show large distinct hysteresis, a clear multiple branching structure with a periodic voltage jump and the edge structure, which represents the superconductive gap. On reducing the number of the intrinsic stacked junctions, the estimated superconductive gap value increases. The thinnest stack exhibits theI–Vcharacteristic of a single junction. The value of the superconductive gap estimated from the single junction sample is about 75 meV at 4.2 K. The obtainedI–Vcurve is explained quite well by assumingd_x²-y²symmetry for the superconductive order parameter without the term of gap suppression.