Epitaxial YBCO/STO/YBCO trilayers have been grown on (100) SrTiO3 substrates by insitu PLD technique. The resulting trilayer consists of 80 nm thickness YBCO bottom and top film, respectively and a 33 nm thickness STO interlayer. The x-ray measurements show that both the YBCO and STO films were epitaxially grown with c-and a-axis, respectively perpendicular to the substrate surface. The rocking curve of the (005) YBCO peak has a FWHM of 0.36°, indicating a small mosaic spread of these films. The SEM micrographs of the YBCO top layer have revealed that the surface exhibits two kinds of irregularities: voids and droplets. The voids have a circular shape with an average diameter of about 200 nm, while the droplets have a nearly spherical one with about one micron in diameter and a density of 107 cm-2. TEM analysis have not revealed the pinholes or short circuits in the trilayer structure. The crystalline structure of the interface between the substrate and the YBCO bottom layer was investigated by high resolution electron microscopy (HREM). © 1997 Academic Press Limited.

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