Tunnel spectra for Al/Al-oxide/Ni80Fe20 junctions under the superconducting transition temperature of Al films

Abstract Superconductor/insulator/metal (S/I/M) tunnel junction can be used as an indicator of junction quality. For S/I/M junction, zero-bias conductance (ZBC) should be close to zero. However, leakage conductance increases the ZBC values. We measured the ZBC values of the Al/Al-oxide/Ni 80 Fe 20 junctions prepared with various oxidation processes. For strong plasma oxidation (high applied power), most of the junctions showed low ZBC. However, ZBC increased with decreasing power of oxidation. It is considered that oxidation proceeds homogeneously for strong oxidation, compared with weak oxidation process.