High-quality superconducting thin films of Bi₂Sr₂Ca₂Cu₃O_x grown in situ by metalorganic CVD

Abstract

THE Received 28 November; accepted 5 December 1991. superconducting copper oxide system Bi–Sr–Ca–Cu–O (BSCCO) has attracted much attention owing to its high transition temperatures T_c and its stability on exposure to air, relative to the corresponding properties of the Y–Ba–Cu– O system. But despite intense effort, growth techniques capable of yielding as-deposited films with high T_c and high critical current density, J_c, have not yet been forthcoming. Here we report the preparation and properties of c-axis-oriented single-phase Bi₂Sr₂Ca₂Cu₃O_x films grown in situ without post-annealing by metalorganic chemical vapour deposition (MOCVD). Our films have the highest T_c and J_c at 77 K reported so far for BSCCO films grown in situ; one film had a zero-resistance T_c of 97 K, and a J_c of 3.8 × 10⁵ A cm⁻² at 77 K in zero magnetic field. This film showed little degradation of J_c in magnetic fields of up to 8 T applied parallel to the crystallographic a–b plane. The magnetic-field dependence of J_c and observed surface morphologies strongly suggest that these as-grown films have no weak links, which is a promising characteristic for device applications.