Growth of DyBa₂Cu₃O₇__x Thin Films on Vicinal (100) SrTiO₃ Substrates

We report studies of the initial stages of epitaxial growth of DyBa₂Cu₃0₇ _ _{x films}on vicinal (100) SrTiO₃substrates using in situ reflection high energy electron diffraction (RHEED), transmission electron microscopy, and atomic force microscopy. Two sets of substrates, with misorientations of 2.2° and 4.4° off (100) towards (110) were used. These substrates were prethinned and annealed prior to deposition. DyBa₂Cu₃O₇ films were grown by ozone-assisted molecular beam epitaxy. The annealed substrates were reconstructed and had stepped surfaces. Films nucleating preferentially at the steps giving rise to an interconnected network of islands, as observed in plan view transmission electron microscopy. In situ RHEED showed intensity oscillations of the specular spot consistent with such an interpretation, and exhibited behavior dominated by surface diffusion. The higher density of nucleation sites on vicinal surfaces appears to reduce the fraction of a-axis outgrowths. The films grown on vicinal substrates also exhibit a high degree of orthorhombicity. No relationship between RHEED oscillation time periods and the completion of a unit cell of film was found, contrary to observations reported in the literature.