ELECTRICAL TRANSPORT-PROPERTIES OF JOSEPHSON-JUNCTIONS WITH A NB/AU/PI/(PB-BI) STRUCTURE

We fabricated tunnel junctions with structures of Au/PI/Pb and of Nb/Au/Pl/(Pb-Bi) incorporating high-quality and ultrathin polyimide (PI) Langmuir-Blodgett (LB) films and then examined the electrical transport properties of the junctions. The inelastic electron tunneling spectroscopy (IETS) spectra of the Au/PI/Pb junctions reveals that the inelastic electron tunneling process accompanied by the energy loss due to the coupling of tunneling electrons with the vibrational modes of polyimide does not make a significant contribution. For Nb/Au/PI/(Pb-Bi) Josephson junctions, we obtained typical I-V characteristics of a weakly coupled superconductor.