Microstructural changes in epitaxial YBa2Cu3O7−δ thin films due to creation of O vacancies

Structural and transport properties of YBa2Cu3O7−δ thin films subjected to different heat treatments and, consequently, having different O vacancy contents are investigated. It is observed that lattice parameters of the films follow the trend of the bulk material, indicating that either the additional stresses created in c-axis oriented films by O vacancies are negligibly small or they are relaxed at elevated temperatures. In addition, heat treatment under relatively low O2 partial pressures, used to create O vacancies, leads to considerable reduction in local variations of lattice spacings in YBa2Cu3O7−δ thin films.