Stacked Josephson Junction Based on Nb/Si Superlattice

We report on the technology and basic electrical properties of ten-fold stacked Nb/Si/Nb Josephson junction (JJ). The problem of making a large number of stacked JJs with identical properties was solved by metallic superlattice preparation technology. The uniformity of Si barriers thickness was examined by low angle X-ray diffraction and cross-sectional transmission electron microscopy. To prevent pinholes in the Si barriers the Nb/Si superlattice was sputtered at the regime at which smoothing of interfacial roughness occurs. The stacked junction exhibit both ac and dc Josephson effects. In the Ic(B) diffraction pattern there is an extra periodicity of about 2–3 G in addition to a larger period of about 21 G.