Properties of the interfaces in the YBa2Cu3Ox/Au and Tl2Ba2CaCu2Oy/Au heterostructures

The YBa2Cu3Ox (YBCO)/Au and Tl2Ba2CaCu2Oy(TBCCO)/Au sandwich-type heterostr uctures were studied with the aim to enhance the interface quality of high temperature superconductor (HTS) in contact with a normal metal which is fr equently used in cryoelectronic devices. To characterize the superconductin g properties of thin films and interfaces of superconductor/normal metal (S N) heterostructures, the resistance vs. temperature(R - T) dependences, cur rent-voltage characteristics (I - V) and dI/dV - V characteristics were mea sured. The YBCO/Au heterostructures exhibit tunnel properties due to the ex istence of the so-called native barrier created from oxygen depleted YBCO s urface layer. Our results show that the properties of YBCO based planar tun nel junctions are strongly influenced by the state of superconductivity at the SN interface. On the other hand, in TBCCO/Au heterostructures a direct metallic contact is realized in the most cases. Our investigations show tha t the degradation of TBCCO/Au interface is negligible and no native oxide b arrier on the surface of TBCCO film was observed. These results confirm tha t the surface of TBCCO film in close contact with Au is much more stable in comparison with YBCO films and therefore the TBCCO films are more suitable for the preparation of HTS planar structures and tunnel junctions.