Oscillations of properties of thin superconducting films on variation of coating thickness

Superconducting double- and triple-layer film systems were obtained by a method of successive condensation in superhigh vacuum on dielectric substrates cooled to liquid gallium temperatures. Thin (30 - 100 A) Pb, Ca, Mo, Re films were used as a superconducting layer. Semiconductors (C,Se,Si,Ge), semimetals (Bi) and metals (As,Zu,Al,Ti,Ga, Pb,Mo) served as a coating material. Studied were the dependence of the superconducting transmission Tc on temperature and residual resistance Rsub(N) on the coating layer thickness. It is found that with increasing the coating thickness of the layer the character of Tc and Rsub(N) variation may be oscillated or monotonic depending on the combination of the condensed materials. The oscillating period is in the order of 10 A, the oscillation amplitude in the first extremum being in inverse proportion to the superconducter film thickness. It is important that the coating of different superconductor films by one material changes the investigated relations in a quantitatively different way. Pb and Ga films with Ge coating possess the oscillating character of the Tc(dsub(Ge)) relation with the initial growth or reduction of Tc, respectively, whereas the Tc(dsub(Ge)) relation of Mo film is of monotonic character