Josephson Effect in MgB2/Pd/Nb Trilayer Josephson Junctions

Abstract

This paper reports fabrication techniques and results of MgB₂/Pd/Nb trilayer Josephson junctions. The MgB₂ bottom electrode was co-evaporated by molecular beam epitaxy (MBE) technique from both magnesium and boron sources at a low substrate temperature ~ 300 °C, while the interlayer and the top niobium electrode (Pd/Nb bilayer) were deposited ex-situ using RF sputtering. The junctions exhibited  and  Josephson effect as well as a modulation of the critical current in a magnetic field applied in a direction normal to the junction plane. Fractional and integer Shapiro steps were observed at voltages corresponding to the frequency of the applied microwave radiation field. The  products of the junctions compare well with the previously reported values. The results suggest that it should be possible to fabricate all-MgB2 and MgB2 as one of the electrodes Superconductor/Normal/Superconductor (SNS), Superconductor/Insulator/Superconductor (SIS) or even Superconductor/Ferromagnet/Superconductor (SFS) tunnel junctions with interesting characteristics and for various applications.

Keywords: MgB₂, all-MgB₂, Josephson Tunnel junctions, trilayer devices, Niobium.