Compositional effects on plasma-enhanced metalorganic chemical vapor deposition of YBa2Cu3O7−x thin films

Abstract

Epitaxial YBa₂Cu₃O_7−x superconducting thin films with a zero resistance transition temperatures of about 90 K have been prepared, in situ, on LaAlO₃ by a plasma‐enhanced metalorganic chemical vapor deposition process at a substrate temperature of 670 °C in 1 Torr partial pressure of N₂O. The composition of the films was varied systematically to investigate the effect of changes in the Ba/Y and Cu/Y ratio on the film properties. The results indicated that superconducting current densities exceeding 10⁶ A/cm², measured at 77 K by a transport method, could be obtained on films with an anomalously wide range of film compositions. Excess Cu (up to 60%) and deficiency in Ba (down to 30%) from their stoichiometric values did not significantly degrade the superconducting properties of the films. As the composition approached the Y‐Ba‐Cu ratio of 1‐2‐3, an improvement in surface morphology and a decrease in superconducting transition temperature were found.