A low temperature process of vacuum codeposition at 550 °C was used to prepare superconducting Y-Ba-Cu-O thin films on Si substrates without a buffer layer. A zero resistance critical temperature Tce as high as 81.5 K was reached without further high-temperature post-annealing treatment. The surface morphology of films has a granular or porous character dependent on substrate temperature. The atomic emission spectroscopy shows the diffusion of Si from the substrate into the films at the level of several atomic percent.
Temperature dependence of resistance R(T) and critical transport current I c (T) was measured for high-Tc YBa 2 Cu 3 O x granular thin films prepared by vacuum co-evaporation. The results are interpreted in terms of superconductor-constriction-superconductor (ScS) or superconductor-normal metal-superconductor (SNS) models, shown to be more adequate than the superconductor-insulator-superconductor (SIS) one. The films with nearly the same superconducting phase transition can exhibit both metallic (dR/dT>0) or semiconductor (dR/dT<0) behavior at T>Tcon. This is ascribed to intragranular defects which are shunted below T con .
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