Preparation of very large YBCO films on single- and polycrystalline substrates

High quality YBa₂Cu₃O₇ thin films on areas of up to 9″ in diameter have been grown by reactive thermal co-evaporation using a rotating substrate holder. A scanning inductive j_c probe is used to monitor the homogeneity of critical current densities which are typically greater than 2 MA/cm₂. The same technique also allows a double sided deposition for filter applications. Surface resistance values are found to be below 500 μΩ at 10 GHz. On biaxially aligned buffer layers on polycrystalline substrates j_c values of 1.4 MA/cm₂ are achieved at 77 K as well. We have also studied the properties of Nd_1-xBa_2+xCu₃O₇ films grown with the same system.