Reduction of low-frequency 1/f noise in Al-AlOx-Al tunnel junctions by thermal annealing

TL;DR

This study demonstrates that vacuum annealing of Al-AlOx-Al tunnel junctions at 400°C significantly reduces 1/f noise, with temperature-dependent behavior suggesting a decrease in charge trapping sites within the barrier.

Contribution

It shows that thermal annealing effectively reduces low-frequency noise in tunnel junctions, providing insights into noise mechanisms and potential fabrication improvements.

Findings

1/f noise decreased by up to an order of magnitude after annealing

Noise temperature dependence is linear below 100 K

Annealing reduces charge trapping sites in the barrier

Abstract

We report that annealing Al-AlOx-Al tunnel junctions in a vacuum chamber at temperature of 400C reduces the characteristic 1/f noise in the junctions, in some cases by an order of magnitude. Both ultra high vacuum and high vacuum fabricated samples demonstrated a significant reduction in the 1/f noise level. Temperature dependence of the noise was studied between 4.2 and 340 Kelvin, with a linear dependence below 100 K, but a faster increase above. The results are consistent with a model where the density of charge trapping two level-systems within the tunneling barrier is reduced by the annealing process.