PREDICTIONS ABOUT THE PROXIMITY EFFECT IN A NBN YHX BILAYER/

It is shown that the properties of the NbN/YHx bilayer system make it very suited for a proximity-effect study. The material parameters of Y Hx, in particular the resistivity and correspondingly the diffusion co nstant, change reversibly by orders of magnitude by simply varying the hydrogen content x. Measurement of the critical temperature and the p arallel and perpendicular upper critical fields would form a delicate test of the presently available proximity-effect theories. Also the re latively uncertain value on the density of states at the Fermi energy in NbN could be determined better. The predictions about the critical quantities are based on the Takahashi-Tachiki theory which is valid fo r dirty metallic structures. The calculations show that the thickness of the superconducting NbN layer should be close to the critical layer thickness, around 12 nm. For the nonsuperconducting material YHx thic ker layers, up to a 500 nm, are profitable for producing a substantial effect.