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

作者：Julin J K; Maasilta I J^*

来源：Superconductor Science and Technology, 2016, 29(10): 105003.

DOI：10.1088/0953-2048/29/10/105003

• superconducting tunnel junction
• niobium
• NIS junction
• thermometry
• sub-gap current

We have developed a technique to fabricate sub-micron, 0.6 mu m x 0.6 mu m 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 T-C similar to 7.5 K and the gap Delta similar to 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 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.

• 出版日期2016-10