Role of oxygen vacancies in the flux-pinning mechanism, and hole-doping lattice disorder in high-current-density YBa2Cu3O7-x films.

Critical-current measurements on epitaxial YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} films with 0{le}{ital x}{le}0.2 demonstrate that chain-site oxygen vacancies are not strong flux-pinning centers in high-{ital J}{sub {ital c}} films. {ital J}{sub {ital c}} decreased steadily with increaing {ital x}, consistent with the predicted, monotonic dependence of pinning energy on mobile-charge-carrier density in strongly pinned systems. A correlation between the oxygen pressure {ital p}{sub O2} during high-temperature growth and subsequent response to low-temperature variation of {ital x} was observed for {ital T}{sub {ital c}}. Specifically, films grown at low {ital p}{sub O2}=0.000 26 atm appeared overdoped with holes after oxidation at {ital p}{sub O2}=1.0 atm, indicative of hole-doping defect formation at low initial oxygen contents.