Abstract
Epitaxial cerium oxide (CeO/sub 2/; thickness: 40 nm) buffer layers were deposited on large area (maximum size 10/spl times/30 cm/sup 2/) R-cut single-crystal sapphire (/spl alpha/-Al/sub 2/O/sub 3/) substrates by double electron-beam guns. Substrate heater-and-holder system was modified to maintain the substrate temperature uniform over the large area during deposition. Oxygen gas of a pressure 4/spl times/10/sup -2/ Pa was introduced to keep radio frequency plasma. When the substrate temperature was controlled in the range 640/spl deg/-700/spl deg/C, the CeO/sub 2/ buffer showed a complete [001] orientation and very smooth surfaces by x-ray diffraction analysis and atomic force microscopic observations, respectively, in the whole area of the large size substrates. These buffer layers without post-deposition annealing were quite suitable for preparing YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) films by a metal-organic deposition (MOD) using a metal acetylacetonate-based solution. The average critical current density of the 210-nm-thick MOD-YBCO film was in excess of 2.6 MA/cm/sup 2/ measured by an inductive method at 77.3 K.
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