Interfacial structures of YbBa_2Cu_3O_(7-δ) superconducting films deposited on SrTiO_3(001) substrates by the dipping-pyrolysis process

摘要

YbBa_2Cu_3O_(7-δ) precursor films and final films formed on SrTiO_3(001) substrates by the dipping pyrolysis process were characterized by transmission electron microscopy. The YbBa_2Cu_3O_(7-δ) precursor films were fabricated by two different heat treatments with changing the heating rate. As a result of this, we found that an amorphous precursor film was produced by rapid heating up to 698 K; in contrast, a polycrystalline precursor film was produced by slow heating. By heating at 998 K, the former film became a c-axis oriented YbBa_2Cu_3O_(7-δ) film with a thickness of 100nm and showed a sharp resistive transition around the critical temperature. However, the latter one was a polycrystalline film containing randomly oriented Yb123 and other crystals even after heating it at 998 K. This polcyrystalline film exhibited a broad transition. In this paper, the effects of the heating rate were investigated from the interfacial structures for achieving the epitaxial growth of YbBa_2Cu_3O_(7-δ) film and the good superconducting properties.