Effects of the initial heat-treatment conditions on microstructures of YbBa2Cu3O7-δ superconducting final films deposited on SrTiO3(001) substrates by the dipping-pyrolysis process

We investigated by transmission electron microscopy the relationship between the initial heat-treatment conditions and the microstructures of YbBa2Cu3O7-delta superconducting final films deposited by a dipping-pyrolysis process on SrTiO3((001) single crystal substrates. An amorphous precursor film was prepared by heating rapidly up to 425 degrees C. By heat-treating at 725 degrees C, this him became a c-axis oriented YbBa2Cu3O7-delta film with a thickness of 100 nm, and showed a sharp resistive transition around the critical temperature (T-c). On the other hand, a polycrystalline precursor film was produced by healing slowly. This film did not give rise to an epitaxial film, but to a YbBa2Cu3O7-delta polycrystalline film with a grain size of about 200 nm, and exhibited a broad transition. Therefore, the initial heat-treatment conditions and the microstructures of the precursor films are important for the epitaxial growth and superconducting properties of the final YbBa2Cu3O7-delta films.