Effects of silver and gold on the YBaCuO superconducting thin films with the use of Ag/Cu/BaO/Y2O3 and Au/Cu/BaO/Y2O3 structures

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Abstract
Superconducting YBaCuO films have been fabricated from the Ag/Cu/BaO/Y2O3 and Au/Cu/BaO/Y2O3 layer structures on MgO substrates. Compared to those using only the Cu/BaO/Y2O3 structure, the addition of a silver layer to the starting structures improves the film resistances, especially at reduced annealing temperatures, allowing the study of the dependence of the superconducting transition on the annealing temperatures between 900 and 750 °C. Zero resistance is observed at 80 K for the Ag/Cu/BaO/Y2O3 structure annealed at 900 °C. The use of a gold layer, on the other hand, reduces the temperature for zero resistance to 75 K for a similarly annealed film. All the superconducting films are composed of the YBa2Cu3O7 and the Y2BaCuO7 phases, with starting compositions off that of the former. Structural and morphological analysis of the films is performed to explore the roles of silver and gold in the films formed.