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Low-Tc Josephson junctions with tailored barrier

M. Weides, C. Schindler, H. Kohlstedt

cond-mat.supr-conarXiv:cond-mat/0612164

Abstract

Nb/Al2O3/Ni0.6Cu0.4/Nb based superconductor-insulator-ferromagnet-superconductor (SIFS) Josephson tunnel junctions with a thickness step in the metallic ferromagnetic 0.60.4 interlayer were fabricated. The step was defined by optical lithography and controlled etching. The step height is on the scale of a few angstroms. Experimentally determined junction parameters by current-voltage characteristics and Fraunhofer pattern indicate an uniform F-layer thickness and the same interface transparencies for etched and non-etched F-layers. This technique could be used to tailor low-Tc Josephson junctions having controlled critical current densities at defined parts of the junction area, as needed for tunable resonators, magnetic-field driven electronics or phase modulated devices.

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