Large-area, two-sided superconducting YBa2Cu3O7−x films deposited by pulsed laser deposition

Abstract

The in situ excimer‐laser deposition process is demonstrated, for the first time, to be an effective technique for producing superconducting films on both sides of substrate wafers of up to 5 cm in diameter. By exploiting the directed nature of the laser produced plume and controlling its off‐axis composition, thickness and stoichiometric variations of less than ±5% have been obtained over the entire surface. Coatings on 5‐cm‐diam LaAlO₃ substrates have uniform transition temperatures of ≥ (R18)90 K on both sides, with a critical current density at 77 K and zero field of 2.5×10⁶ A/cm². The 10 GHz surface resistance for samples cut from a 5 cm wafer is 40–60 μΩ at 4 K.