Homoepitaxial YBa2Cu3O7-delta SNS junctions with normal layers of YBa2(Cu1-xFex)(3)O7-delta, YBa2)(Cu1-xZnx)(3)O7-delta, and PrBa2Cu3O7-delta grown on (001)YBa2Cu3O7-delta single crystal substrates

摘要

We have studied three different homoepitaxial YBa2CU3O7-delta (YBCO) trilayer SNS junctions grown on (0 0 1) YBCO single crystal substrates with nominally 90 nm thick normal layers of YBa2(Cu1-xFex)(3)O7-delta,YBa2(Cu1-xZnx)(3)O7-delta, and PrBa2CU3O7-delta (PBCO). Fe-doped YBCO SNS junctions show clear weak link characteristics with a normal Fraunhofer diffraction pattern. The 32 x 32 mum(2) junction shows a high value of IcRn product, 255 muV, at 6.71 K irrespective of low current density J(c) = 28.3 A/cm(2). On the other hand, Zn-doped YBCO or PBCO SNS junctions shows flux-flow type I-V characteristics. The improvement of IcRn product, 255 muV, of the Fe-doped YBCO SNS junctions comes from high value of R-n = 0-88 Omega to compensate low value of I-c = 290 muA by the improvement of surface morphology of homoepitaxial YBCO SNS structures. The above different device characteristics will be ascribed to the large differences of surface morphology of normal layers or diffusion of Fe and Zn in YBCO layers. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 26]