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arXiv · 1610.05903

Applications and non-idealities of submicron Al-AlOx-Nb tunnel junctions

Juhani Julin·Ilari Maasilta
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Abstract

We have developed a technique to fabricate sub-micron, 0.6 um x 0.6 um 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) configuration. 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.

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Juhani Julin, Ilari Maasilta. 2016-10-19. Applications and non-idealities of submicron Al-AlOx-Nb tunnel junctions. https://doi.org/10.1088/0953-2048%2F29%2F10%2F105003

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