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

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.