Different relaxation mechanisms of epitaxial strain in YBa[sub 2]Cu[sub 3]O[sub 7-δ] films deposited on SrTiO[sub 3] and LaAlO[sub 3].

We present a study of strain relaxation mechanisms in epitaxial c -axis YBa[sub 2]Cu[sub 3]O[sub 7-δ] (YBCO) films deposited on SrTiO[sub 3] (STO) and LaAlO[sub 3] (LAO). A combination of high-resolution transmission electron microscopy and electron back-scattered diffraction in scanning electron microscopy has shown that a considerable amount of 90° tilted small domains exist in films grown on LAO while only planar and/or linear defects are observed in strain-relaxed films on STO. The 90° tilted domains, which have very limited influence on the superconducting characteristics of YBCO, account for the full relief of epitaxial strain in films on LAO. As the strain relaxation originated from different stages of the film deposition, this study may also explain the different crystalline qualities, surface morphologies, and some of the transport properties of YBCO films on STO and LAO. [ABSTRACT FROM AUTHOR]