Electrical and structural properties of Nb/Al/Nb overdamped Josephson junctions

Superconductor-normal metal-superconductor (SNS) Josephson junctions are gaining interest in many fields, related to superconducting electronics. Their main advantages are the high critical current density and non-hysteretic I-V characteristic. We have studied Nb/Al/Nb SNS junctions, where the combined effects of the thickness and deposition rate of the Al barrier play a relevant role in determining the electrical behaviour of the junction. The increase of the Al deposition rate from 0.5 to 5 nm/s increases the surface roughness of the junction by a factor of two, with a corresponding variation of the current density and of the ICRN product from 10(6) to 10(3) A/cm(2) and from 100 muV to 1 mV, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.