Critical parameters in the single-target sputtering of YBa2Cu3O7

The critical parameters in the single-target magnetron sputtering of YBa₂Cu₃O₇ have been identified and sufficiently optimized to allow the reproducible deposition of films with T_c's of ≳90 K and J_c's of ≫ 10⁶ A/cm² at 77 K. It was found that during film growth the bombardment of the YBa₂Cu₃O₇ by energetic particles must be minimized and also a stronger oxidizing agent than molecular oxygen must be present to obtain films with these properties. Otherwise, films are deposited that, by x-ray diffraction and energy dispersive x-ray spectroscopy analyses, are indistinguishable from the highest-T_c 1:2:3 stoichiometric material but which have critical temperatures of ≪90 K. Films need not have 1:2:3 overall stoichiometry to have optimum superconducting properties. In such cases the excess elements are present as second-phase particles.