Tailored Thin Films of Superconducting Bi-Sr-Ca-Cu Oxide Prepared by the Incorporation of Exotic Atoms

Abstract

Layer-by-layer successive deposition utilizing laser ablation has been applied to the site-selective substitution of +1, +2 and +3 ions having different ionic radii at the Ca and Sr site of Bi₂Sr₂Ca₁Cu₂O_y superconducting films. The substitutions at Sr and Ca site exhibit quite different behaviors in the superconductivity and the structural parameters. For the substitution of larger ions at the Ca site, lattice parameter c increases showing the higher Tc value, while the substitution of at the Sr site does not elongate the c axis and does not increase the Tc. These changes have been explained by the structure models, and the correlation between Tc and the lattice parameters is explained by the changes of the distance between CuO₂ layers, indicating the importance of the interaction between CuO₂ layers.