Interface-Treated Josephson Junctions in Trilayer Structures

We fabricated double interface-treated Josephson junctions with vertically-stacked geometry based on the high temperature superconductor YBCO. The junctions have a superconductor -insulator -superconductor -insulator -superconductor structure. If the intermediate layer is thin enough, the two junctions are coupled inductively through the intermediate layer, and the two junctions switch simultaneously. The double junctions with 30 nm thick intermediate layer exhibited resistively-shunted-junction characteristics and had no kinks in their curves. In a typical chip, an average of the critical current density was 1.65 kA cm 2 with 1 spread of 14.6%. The nominal c n product for a double junction was 2.43 mV with 1 spread of 5.72%. This c n product is 1.5-2 times larger than that of the single vertically-stacked junction having similar critical current density. These experimental results suggest the simultaneous switch of the two junctions. We expect that higher nominal c n products would be obtained after choosing appropriate process parameters, because the c n products of our previous single junctions have reached 2 mV.

Section: Methodsmentioning

confidence: 99%

Fabrication of Inductively-Coupled Double-Josephson Junctions Using High-Temperature Superconductors

Kimura

Watanabe

Sugimoto

et al. 2007

“…Details of the junction fabrication process is found elsewhere [4], [5]. Here we describe the sample fabrication process for the TEM observation.…”

Section: Methodsmentioning

confidence: 99%

“…Interface engineering technique provided a promising way to high quality junctions, and has been applied to ramp-edge junctions [1]- [3]. The authors applied this technique to stacked-type junctions, and obtained high product of 2.1 mV (at 4.2 K) and fairly low spread of junction properties about 10% [4] current was often observed, which was considered to arise from the superconducting leak paths in the barrier. The authors introduced a process of (PGO) doping to the barrier to eliminate such leak paths [5].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Barrier in Vertically-Stacked Interface-Treated Josephson Junctions

Inoue

Yoshinaga

Wakita

et al. 2005

The authors have investigated the structure and the composition of the barrier in YBCO vertically-stacked-type interface-treated Josephson junctions by TEM and TEM-EDS. The barrier was formed by the Ar ion milling of the base YBCO electrode surface and the subsequent annealing. For a sample treated with accelerating voltage ( acc ) of 1300 V, we observed Y 2 O 3 phases in the barrier. In contrast, for a sample with acc = 700 V, we could observe few Y 2 O 3 phases. Our TEM observation suggested that junctions with higher c fabricated with lower acc would have thinner and more uniform barriers. In addition, the composition of the barrier was Y-rich and Cu-poor, and such deviation decreased with decreasing acc . These tendencies well correspond to the results for ramp-edge-type junctions reported so far.

“…Until now, many efforts have been exerted in the preparation of heteroepitaxial sandwich-type junctions made of HTS. For the c-axis YBa2C~307.x (YBCO) system, SrTi03 [ 11, BizSr2CuO6, (Bi-2201) [2], Y203 [3], and PrBazCu307, (PBCO) [4], [5] have been used as non-superconducting barrier materials. On the other hand, PBCO [6], [7] and PrGa03 [8] have been adopted for the a-axis YBCO system.…”

Section: Introductionmentioning

confidence: 99%

Preparation of superconductive Y-Ba-Cu-O/Bi-Sr-Ca-Cu-O heteroepitaxial bilayer films by Nd:YAG laser ablation

Uchiyama

Wang²

2001

Absrract-Here we report for the first time the heteroepitaxial growth of as-deposited superconductive YBa2C~307-x (YBCO)/Bi2Sr2CaCu208, (Bi-2212) and Bi-2212 /YBCO bilayer films on MgO (100) substrates by using the 4'h harmonics of a Nd:YAG pulsed laser beam. The Bi-2212 thin films had single-phase crystallinity and a zero resistance temperature (Tco) of 71.4 K. Under similar preparation conditions, YBCO thin films showed single phase and Te0 = 88.5 K. The YBCOIBi-2212 bilayer films grown with an in situ process showed oaxis orientation and single phase for both YBCO and Bi-2212. Moreover, X-ray pole figures indicated that YBCO/Bi-2212 and Bi-2212/YBCO bilayer films grow heteroepitaxially with in-plane orientation of the Bi-2212 [loo] direction parallel to the [110] direction of YBCO.