Fabrication of stable and reproducible sub-micron tunnel junctions

TL;DR

This study demonstrates a fabrication process for sub-micron Al/AlOₓ/Al tunnel junctions that achieves high stability and reproducibility through substrate cleaning and controlled thermal treatments, with minimal resistance variance.

Contribution

The paper introduces a fabrication protocol that ensures stable, reproducible sub-micron tunnel junctions with low resistance variance, suitable for advanced applications.

Findings

Aggressive substrate cleaning yields stable oxide barriers.

Reproducibility confirmed across large junction ensembles.

Thermal treatments influence junction barrier properties.

Abstract

We have performed a detailed study of the time stability and reproducibility of sub-micron $Al/AlO_{x}/Al$ tunnel junctions, fabricated using standard double angle shadow evaporations. We have found that by aggressively cleaning the substrate before the evaporations, thus preventing any contamination of the junction, we obtained perfectly stable oxide barriers. We also present measurements on large ensembles of junctions which prove the reproducibility of the fabrication process. The measured tunnel resistance variance in large ensembles of identically fabricated junctions is in the range of only a few percents. Finally, we have studied the effect of different thermal treatments on the junction barrier. This is especially important for multiple step fabrication processes which imply annealing the junction.