Bilayer fabrication and B-site cation interdiffusion in the Bi–Sr–Ca–Cu–O/Bi–Sr–Co–O system

Abstract

The bilayer system of Bi 2Sr 2Ca n−1 Cu n O y and Bi 2Sr 2CoO 6.25+ δ thin films grown by molecular beam epitaxy was investigated by X-ray diffraction, reflection high-energy electron diffraction, and d.c. resistivity measurement. We found that a diffusion behavior is qualitatively different among Bi 2Sr 2Ca n−1 Cu n O y /Bi 2Sr 2CoO 6.25+ δ bilayers ( n=1, 2, 3). In the case of the Bi 2Sr 2CoO 6.25+ δ /Bi 2Sr 2CuO 6+ δ bilayer, it was revealed that Cu in Bi 2Sr 2CuO y and Co in Bi 2Sr 2CoO 6.25+ δ interdiffused and the film became a solid solution of Bi 2Sr 2(Cu 1− x Co x )O y . On the other hand, in the cases of Bi 2Sr 2CaCu 2O 8+ δ /Bi 2Sr 2CoO 6.25+ δ and Bi 2Sr 2Ca 2Cu 3O 10+ δ /Bi 2Sr 2CoO 6.25+ δ bilayers, substitution of Co for Cu was drastically suppressed and the bilayers show superconductivity.