We have measured the low frequency critical current noise in Nb/AlOx/Nb Josephson junctions. Unshunted junctions biased above the gap voltage and resistively shunted junctions biased near the critical current, Ic, have been measured. For both, the spectral density of δIc/Ic, Sic(f), is proportional to 1/f, scales inversely as the area, A, and is independent of Jc≡Ic/A over a factor of nearly 20 in Jc. For all devices measured at 4.2 K, Sic(1 Hz)=2.0±0.4⋅10−12/Hz when scaled to A=1 μm2. We find that, from 4.2 K to 0.46 K, Sic(f) decreases linearly with temperature.
@article{arxiv.0809.3272,
title = {Temperature Dependence of Critical Current Fluctuations in Nb/AlO$\mathrm{_{x}}$/Nb Josephson Junctions},
author = {Shawn Pottorf and Vijay Patel and James E. Lukens},
journal= {arXiv preprint arXiv:0809.3272},
year = {2009}
}