Metalorganic chemical vapor deposition of Bi-Sr-Ca-Cu-O ultrathin films

The metalorganic chemical vapor deposition of Bi-Sr-Ca-Cu-O ultrathin films was performed on single-crystal (100) MgO substrates. An ultrathin film with average thickness of 3.5 nm was found to exhibit the full superconductivity at more than 60 K. The critical current density of a 5-nm-thick film was found to be strongly anisotropic for applied fields parallel and perpendicular to the film plane. In particular, in a field parallel to a film plane, the critical current density was constant up to 6 T even at 50 K, near the critical temperature. From the x-ray-diffraction patterns of ultrathin films prepared at the deposition rates of 3 and 0.3 nm/min, a Bi₂Sr₂CaCu₂O_x (2212) phase was found to be formed at the first stage of deposition regardless of the deposition rate, while a Bi₂Sr₂Ca₂Cu₃O_x (2223) phase was found to be formed in the earlier stage of deposition when the deposition rate was decreased.