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

We report that annealing Al–AlOx–Al tunnel junctions in a vacuum chamber at temperature of 400 °C reduces the characteristic 1/f noise in the junctions, in some cases by an order of magnitude. Both ultrahigh 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 K, 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.