A comprehensive investigation and comparison of the superconducting properties of bilayer and multilayer epitaxial heterostructures of IV–VI semiconductors exhibiting superconductivity at critical temperatures Tc⩽6.5K is carried out. The superconductivity of these systems is due to inversion of the bands in the narrow-gap semiconductors on account of the nonuniform stresses created by the grids of misfit dislocations arising at the interfaces during the epitaxial growth. It is found that Tc and the character of the superconducting transition of bilayer PbTe∕PbS heterostructures depend on the thickness d of the semiconductor layers and are directly related to the quality of the grids of misfit dislocations at the interfaces (the number and type of structural defects in the grids). Substantial differences in the behavior of bilayer sandwiches and superlattices are found. The minimum thickness d at which superconductivity appears is several times larger for bilayer than for multilayer systems. The upper critical magnetic fields Hc2 of the bilayer systems are more anisotropic. For superlattices 3D behavior is observed in the temperature region close to Tc, and with decreasing temperature a 3D–2D crossover occurs. For the bilayer structures 2D behavior starts immediately from Tc, and a 2D–1D crossover is observed, with the sharp divergence of Hc2 that is characteristic of superconducting nets.

We demonstrate, both theoretically and experimentally, that thin dirty superconductor-normal metal bilayer with resistivity of normal metal ρN much smaller than normal-state resistivity of superconductor ρS has unique superconducting properties. First of all the normal layer provides the dominant contribution to the diamagnetic response of whole bilayer structure in wide temperature interval below the critical temperature due to proximity induced superconductivity. Secondly, the presence of the normal layer may increase the critical current Ic in several times (the effect is not connected with enhanced vortex pinning), provides strong temperature dependence of both Ic and effective magnetic field penetration depth even at temperatures much below the critical one and leads to the diode effect in parallel magnetic field. Besides of general interest we believe that the found results may be useful in construction of different kinds of superconducting detectors.

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YBa 2 Cu 3 O 7−x epitaxial films have been studied by near-field nonlinear microwave and low-temperature scanning microscopies. A correlation between the half-widths of peaks in the temperature dependences of third-harmonic power, electron-beam-induced voltage, and the size of the x-ray coherent region ͑average grain size͒ was revealed. According to a two-phase model, the nonlinear microwave response is determined by intragrain vortex pinning at large grain sizes and by pinning at intergrain boundaries at small grain sizes. The results of model calculations suggest that a threefold increase in the average grain size can result in a 100-fold decrease in the nonlinear coefficient of YBa 2 Cu 3 O 7−x films.