A fabrication technique for Nb-Al2O3-Nb Josephson tunnel junctions is described that is an alternative to the trilayer method generally used. At 4.2 K the magnitude of the low-frequency noise in the critical current I0 of four junctions with areas 𝒜 ranging from 7.8 to 115 μm2 was characterized by S1/2I0𝒜1/2/I0 =(14±6)pA μm/μA Hz1/2, where SI0 is the spectral density of the excess noise at 1 Hz. The noise power spectrum of one 3×3 μm2 junction exhibited a Lorentzian feature associated with the emptying and filling of a single trap in the barrier. The low level of noise makes these junctions attractive for use in superconducting quantum interference devices.
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Savo et al. (1987) studied this question.
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