Cerium oxide (CeO2) buffer layers for preparation of high-Jc YBCO films on large-area sapphire substrates (30 cm x 10 cm) by coating pyrolysis

摘要

Epitaxial cerium oxide (CeO2, 40 nm) buffer layers were deposited on large-area (30 cm x 10 cm) R-plane single-crystal substrates of sapphire (alpha-Al2O3) by an electron-beam gun in a vacuum chamber. Oxygen gas of a pressure 4x10(-2) Pa was introduced and was activated by radio frequency plasma. When the substrate temperature was controlled at 670 30 degreesC, the CeO2 buffer layers were found to have a complete (0 0 1) orientation and very smooth surfaces (average surface roughness: 0.5 nm) by X-ray diffraction analysis and atomic force microscopic observations, respectively, for all over the surface of the large-area substrates. These buffer layers were quite suitable for preparing YBa2Cu3O7 (YBCO) films using a metal acetylacetonate-based solution by a coating-pyrolysis process. The average critical current density of the 210-nm thick YBCO film was in excess of 2.6 MA/cm(2) measured by an inductive method at 77.3 K. (C) 2004 Elsevier B.V. All rights reserved.