CHARACTERISTICS OF INTRINSIC JOSEPHSON-JUNCTIONS IN A THIN STACK ON BI-2223 THIN-FILMS

We have successfully fabricated a small thin stack with a small number of intrinsic junctions on (Bi, Pb)(2)Sr2Ca2Cu3O10+x thin films. Mesa structures with the junctions are fabricated on the surface of high-qu ality films prepared by rf-sputtering and subsequent heat treatment. C urrent-voltage (I-V) responses along the c-axis show large distinct hy steresis, 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 estim ated superconductive gap value increases. The thinnest stack exhibits the I-V characteristic of a single junction. The value of the supercon ductive gap estimated from the single junction sample is about 75 meV at 4.2 K. The obtained I-V curve is explained quite well by assuming d (x)2(-y)2 symmetry for the superconductive order parameter without the term of gap suppression.