Fabrication of electron tunneling junctions on Nb3Ge and ErRh4B4 using artificial barriers of rare earth oxides

Electron tunneling junctions have been prepared on Nb3Ge and ErRh4B4 using artificial barriers of thin oxidized films of sputtered rare earth metals. The junction fabrication technique is simple and fast, and has been used to produce Josephson junctions on Nb and ErRh4B4 which have observed to thermally cycle. Although the process was not optimized in the case of Nb3Ge, it showed promise of eliminating the problems that have in the past prevented quantitative tunneling studies of this compound. Single particle and pair tunneling investigations of the re-entrant superconductor ErRh4B4 suggest that a magnetic structure of semi-macroscopic size can coexist with superconductivity at temperatures near the re-entrant transition temperature