Effect of Sputtering Parameters on Superconducting Properties of GdBaCuO Epitaxial Thin Film Deposited by ICP Method

Thin films of GdBaCuO (GBCO) have been deposited in situ onto LaAlO₃ single crystal substrates by inverted cylindrical sputtering pattern (ICP). The superconductive properties of the thin films' dependence on the substrate temperature and sputtering pressure have been systematically investigated. By optimization of the deposition parameter, high-quality c-axis epitaxial GBCO thin films of T _c0>92 K were reproducibly grown. The T _c of the best sample is as high as 93.2 K. Upon changing the target composition to GdBa₂Cu₄O _y (Gd₁₂₄), it was observed that the samples always show some a-axis oriented films, implying that excess copper would favor a-axis growth in thin films. The superconductivity of the thin films under higher substrate temperature (T _s>800°C) was clearly improved by the procedure of special post-oxygenization at 400°C with an ozone atmosphere. This is very useful for preparing large-area thin films of GBCO.