The proximity and Josephson effects in niobium nitride–aluminum bilayers

Highly disordered thin films of niobium nitride and the specific features of the proximity effect in NbN (S)–aluminum (N) bilayers with a large resistivity ratio, $\rho_{\mathrm{NbN}}/\rho_{\mathrm{Al}}\gg1$, are studied. It is shown that magnetic screening and the critical current Ic of such SN structures significantly increase compared to the S layer. The observed effect is associated with the induced superconductivity in the N layer due to the proximity effect. The Josephson effect is demonstrated in NbN/Al–NbN–NbN/Al variable thickness bridges made of such SN bilayers.