Quantitative texture measurements of YBCO films on various substrates

Abstract

X-ray pole figure measurements are used to investigate epitaxial relations of thin polycrystalline YBa 2Cu 3O 7−δ (YBCO) films on various single-crystal substrates. Films of YBCO were deposited at various temperatures by laser ablation. Basically two orientations were identified, one with the c axes of YBCO normal to the film (C) and one with the a axes of YBCO normal to the film (A). Detailed two-dimensional scans are used not only to establish quantitative ratios between orientations but also to determine overall crystallinity. In general the C orientation is dominant at high deposition temperatures and in thin films, whereas the A orientation prevails at low temperatures and in thicker films. The A—C transition can be well documented in films deposited on (001) LaAlO 3 at various temperatures. On (001) MgO and YZr 2O substrates and at higher temperature, a subsidiary orientation is observed with the c axes parallel to the film but the a axes rotated 45° so that they are parallel to the [110] of the substrate. High crystallinity and dominating C orientations are present for films on CeO 2 coated (012) α-Al 2O 3. In the case of a thick film on YZr 2O the effect of a layered structure on diffraction intensities is documented with C orientations underneath a layer of A orientations. In comparison with orientation determinations by transmission electron microscopy, selected area diffraction or X-ray Laué patterns, X-ray texture analysis as described here provides a quantitative volume average of orientations which is representative of selected regions of the material and can be related to macroscopic properties.