Phase characterization of dysprosium barium copper oxide thin films grown on strontium titanate by molecular beam epitaxy

Abstract

X-ray diffraction, transmission electron microscopy, and /ital in/ /ital situ/ reflection high energy electron diffraction studies of thin epitaxial dysprosium barium copper oxide films grown by oxygen plasma molecular beam epitaxy (MBE) on strontium titanate substrates are presented. A remarkable variety of structure is revealed, making clear both the possibilities and challenges for this growth technique as applied to the cuprate superconductors. The films studied are highly epitaxial, obtained through the use of shuttered molecular beams to encourage the layered structure characteristic of superconducting DyBa/sub 2/Cu/sub 3/O/sub 7/minus//ital x// (''123''). While some of these films are superconducting as deposited, more often they are semiconducting or insulating. The 123-like material in these films has a lengthened c-axis, perhaps due to nonstoichiometry. Phases related to DyBa/sub 3/Cu/sub 2/O/sub /ital x// (the other perovskite) are also very important for epitaxial growth, and display a distinctive signature in the RHEED patterns. Other epitaxial impurity phases including BaCuO/sub 2/ and a new orthorhombic phase are also characterized.