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Application of Josephson effect in sensors, electronic and metrological devices working at temperature of 77 K requires fabrication of efficient and reproducible high temperature superconducting (HTS) Josephson junctions. In order to enhance the performance of HTS junctions, we introduce multilayered approach to YBCO-based step-edge Josephson junction manufacture. Thin YBCO and multilayered YBCO/NdBCO/YBCO films of a similar thickness (\sim210 nm) were grown by a pulsed-laser deposition technique on MgO (100) substrates with artificially created step edge. Large discrepancies of Ic and Rn values were found between these two types of junction. Results of their structural and electrical properties are reported. [ABSTRACT FROM AUTHOR]

Much denser YBa2Cu3O7 (YBCO) superconducting films at least 1 μm thick with smooth surfaces have been obtained after introducing (Y/Nd)BCO multilayered structures. A significant enhancement of current carrying abilities has been achieved in these pulsed laser deposited films. The critical current density (Jc) has been increased by a factor of up to three in the entire field range. The imitation of the (Y/Nd)BCO multilayered structure by using YBCO ‘interlayers’ has also exhibited a considerable improvement in the current carrying ability. Similarities and differences between these two ‘multilayering’ approaches, leading to the observed effects, are discussed. The presence of interfaces even without element variation is likely to be the key to the improvements observed. In order to further promote Jc enhancement, small ‘multilayered’ additions of silver (Ag) to the films and multilayers provide various results: (i) rather strong enhancement for rather thin films and low addition levels, (ii) considerable degradation for large addition levels, and (iii) much less pronounced effect for thicker films. The enhancement of Jc is observed in zero and low magnetic fields, but has almost no effect at higher fields. All these experimental observations are discussed in terms of pinning, transparency and structural modifications introduced during the deposition of the film structures. [ABSTRACT FROM AUTHOR]

Significant differences in superconducting and microstructural properties between two types of MgB2 films prepared by pulsed laser deposition were determined. A very high Hc2 — T slope of 1.1 T/K was achieved in the in situ film. The Jc — H curves of the in situ film also show a much weaker field dependence than that of the ex situ film. The magneto-optical (MO) images show that at 4 K the flux penetrates the in situ MgB2 film through random paths, while for the ex situ film, the flux penetration pattern is mostly repeatable, indicating a defect-controlled flux penetration. Microstructural study (transmission electron microscopy and atomic force microscopy) revealed a relatively big grain size in the ex situ film. The correlation between the super- conducting properties, microstructure and preparation conditions is discussed with regard to the two types of films. [ABSTRACT FROM AUTHOR]