Effect of buffer layers on low-temperature growth of mirror-like superconducting thin films on sapphire

Plasma-assisted laser deposition was used to grow high quality mirror-like superconducting Y-Ba-Cu-O films on sapphire with or without a buffer layer. The buffer layers of MgO, Ag, or BaTiO₃ were also laser deposited. At a deposition temperature of 400-500 °C, the as-deposited Y-Ba-Cu-O films on MgO/Al₂O₃, Ag/Al₂O₃, BaTiO ₃/Al₂O₃, and plain Al₂O₃ substrates were all superconducting at ≳75 K without post-annealing. The orientation of the film and the critical current are both affected by the presence of the buffer layer.