Influence of the Al thickness of Nb/Al-AlOx/Nb Josephson junction on the magnetic field dependence of the Josephson current

• Published in: Physica. C, Superconductivity Superconductivity, 2020-12, Vol.579, p.1353754, Article 1353754
• Main Authors: Kobayashi, Kazuki, Nakayama, Akiyoshi, Abe, Susumu, Watanabe, Norimichi
• Format: Article
• Language: English
• Subjects: Al layer thickness; Aluminum; Current voltage characteristics; Dependence; Diffraction; Diffraction patterns; Fraunhofer pattern; Josephson current; Josephson junctions; Magnetic fields; Magnetism; Nanoparticles; Nb/Al-AlOx/Nb Josephson junction; Niobium; PN junction devices; Thickness
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2020.1353754

•We fabricated Nb/Al-AlOx/Nb Josephson junctions with different Al layer thicknesses.•We investigated the influence of the thicknesses of Al layers on the characteristics of the Josephson junctions.•The Josephson current decreased as the Al layer thickness of the Josephson junction became thicker.•The subpeak of the Fraunhofer diffraction pattern was hardly observed in the Josephson junction with the Al layer thickness of 200 nm. We have fabricated Nb/Al-AlOx/Nb Josephson junctions and have measured their current-voltage characteristics and the two-dimensional magnetic field dependence of the Josephson current. When the external magnetic fields (Hx, Hy) parallel to the junction plane are applied to the Josephson junction from two directions, two Fraunhofer diffraction patterns are observed in the (Hx, Hy) plane. In this study, we have fabricated several Nb/Al-AlOx/Nb Josephson junctions with different thicknesses of Al layer and have investigated the effect of the Al layer thicknesses on the two-dimensional magnetic field dependence of the Josephson current. The thicknesses of the Al layers in the Josephson junctions we fabricated are 5 nm, 25 nm, 50 nm, 100 nm and 200 nm. When the Al layer thickness was 5 nm and 25 nm thick, a subpeak of the Fraunhofer diffraction pattern was clearly observed. However, the subpeak of the Fraunhofer diffraction pattern was not obviously observed as the Al layer got thicker. In particular, when the Al layer was 200 nm thick, the subpeak of the Fraunhofer diffraction pattern was not observed at all.