We report on systematic studies to perform quality controls on planar tunnel junctions realized on high-T c superconductors (HTS). Tunneling spectra of the orthorhombic 90 K and 60 K YBa2 Cu 3O7−δ phases, of the magnetically doped, tetragonal YBa 2( Cu 0.96 Fe 0.04)3 O 7 compound and of the Bi 2 Sr 2 CaCu 2O8 system are analyzed. The traditional, low-bias barrier analysis as well as a number of tests useful to investigate the “status” of the HTS surface layer are carried out. Evidence is given that some anomalous tunneling data can be understood in terms of a Kondo-type scattering between tunneling electrons and magnetic impurities at the interface. The reproducibility of the tunneling spectra for different junction fabrication conditions is also discussed.
Infrared detection with high-[Tc] bolometers and response of Nb tunnel junctions to picosecond voltage pulses