Applications and non-idealities of submicron Al–AlOx–Nb tunnel junctions
Julin, J., & Maasilta, I. (2016). Applications and non-idealities of submicron Al–AlOx–Nb tunnel junctions. Superconductor Science and Technology, 29 (10), 105003. doi:10.1088/0953-2048/29/10/105003
Published inSuperconductor Science and Technology
© 2016 IOP Publishing Ltd. This is a final draft version of an article whose final and definitive form has been published by IOP. Published in this repository with the kind permission of the publisher.
We have developed a technique to fabricate sub-micron, 0.6µm×0.6µm Al-AlOx-Nb tunnel junctions using a standard e-beam resist, angle evaporation and double oxidation of the tunneling barrier, resulting in high quality niobium, as determined by the the high measured values of the critical temperature TC ∼ 7.5 K and the gap ∆ ∼ 1.3 meV. The devices show great promise for local nanoscale thermometry in the temperature range 1 - 7.5 K. Electrical characterization of the junctions was performed at sub-Kelvin temperatures both with and without an external magnetic field, which was used to suppress superconductivity in Al and thus bring the junction into a normal-metal-insulator-superconductor (NIS) con- figuration. We observed excess sub-gap current, which could not be explained by the standard tunneling theory. Evidence points towards materials science issues of the barrier or Nb/AlOx interface as the culprit.