Low-temperature growth of mirror-like superconducting thin films on sapphire

The recently developed process of plasma-assisted laser deposition was used to grow high-quality, mirror-like superconducting Y-Ba-Cu-O films on sapphire, both with and without a buffer layer. At a deposition temperature of 400° C, the as-deposited Y-Ba-Cu-O film on MgO/Al₂O₃ and Ag/Al₂O₃ and Al₂O₃ substrates was superconducting at ≈ 75 K. The orientation of the film and the critical current both depended on the presence of the buffer layer. After suitable patterning, such films should have important applications in microwave electronics.