Temperature Dependence Of Critical Current Fluctuations In Nb/Alox/Nb Josephson Junctions

We 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 I-c have been measured. For both, the spectral density of delta I-c/I-c, S-ic(f), is proportional to 1/f, scales inversely as the area A and is independent of J(c)equivalent to I-c/A over a factor of nearly 20 in J(c). For all devices measured at 4.2 K, S-ic(1 Hz)=2.0 +/- 0.4x10(-12)/Hz when scaled to A=1 mu m(2). We find that, from 4.2 to 0.46 K, S-ic(f) decreases linearly with temperature.