STRUCTURAL AND MORPHOLOGICAL PROPERTIES OF IN-SITU PLD YBCO STO/YBCO TRILAYER/

Epitaxial YBCO/STO/YBCO trilayers have been grown on (100) SrTiO3 subs trates by insitu PLD technique. The resulting trilayer consists of 80 nm thickness YBCO bottom and top film, respectively and a 33 nm thickn ess STO interlayer. The x-ray measurements show that both the YBCO and STO films were epitaxially grown with c- and a-axis, respectively per pendicular to the substrate surface. The rocking curve of the (005) YB CO peak has a FWHM of 0.36 degrees, indicating a small mosaic spread o f these films, The SEM micrographs of the YBCO top layer have revealed that the surface exhibits two kinds of irregularities: voids and drop lets. The voids have a circular shape with an average diameter of abou t 200 nm, while the droplets have a nearly spherical one with about on e micron in diameter and a density of 10(7) 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 mic roscopy (HREM). (C) 1997 Academic Press Limited.