Reflectivity oscillations in superconducting superlattices Nb/SiO2

The reflectivity of superconducting superlattices Nb/SiO₂ was experimentally studied at room temperature in a spectral range 450-5000 cm^-1. It was found that the reflectivity as a function of SiO₂ layer thickness oscillates with a period 3.5 Å. This value coincides with the period of oscillations of the superconducting transition temperature found earlier on these superlattices. We suppose that in both cases the oscillations are due to changes of electron state density. So it is possible to considerably influence the superconducting transition temperature of a superconducting film by making sandwich-like structures using thin dielectric layers.