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Author Ayache, J. ♦ Thorel, A. ♦ Lesueur, J. ♦ Dahmen, U.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ YTTRIUM COMPOUNDS ♦ BARIUM COMPOUNDS ♦ SCANNING ELECTRON MICROSCOPY ♦ JOSEPHSON EFFECT ♦ HIGH-TC SUPERCONDUCTORS ♦ YTTRIUM OXIDES ♦ BARIUM OXIDES ♦ COPPER OXIDES ♦ BICRYSTALS ♦ STRONTIUM OXIDES ♦ TITANIUM OXIDES ♦ GRAIN BOUNDARIES ♦ TRANSMISSION ELECTRON MICROSCOPY ♦ SUPERCONDUCTING FILMS
Abstract The topography and crystallography of YBa{sub 2}Cu{sub 3}O{sub 7{minus}d} (YBCO) bicrystal films grown epitaxially on oriented SrTiO{sub 3} (STO) bicrystals have been characterized by scanning and transmission electron microscopies (SEM and TEM) and atomic force microscopy (AFM). The YBCO films were formed by laser ablation on melt-grown {Sigma}13 STO bicrystals with a misorientation of 24{degree} around the {l_angle}001{r_angle} tilt axis. In agreement with previous reports, TEM analysis revealed that the grain boundary in the film did not always follow the planar substrate grain boundary faithfully, but undulated about the average boundary plane. High resolution electron microscopy observations of the apparently complex undulating boundary structures could be explained as a result of an overlap between different orientation variants of the orthorhombic YBCO film. Cross correlation between SEM, AFM, and TEM imaging gave a clear evidence that an island growth mechanism is responsible for the observed grain boundary structure and morphology for which a schematic model is presented. It is seen that meandering of the YBCO grain boundary (GB) is necessarily coupled to a wide range of inclination of the GB plane in the {ital z} direction. The implications of this interfacial structure for the behavior of GB based Josephson junctions are discussed and compared to models proposed in the literature. It is also seen that inclination of the GB may be responsible for the poor correlation usually found in the literature between calculations and experimental curves of current density J{sub c} versus the GB angle since the most elaborate models proposed up to now take into account only pure tilt GB plane facets, that is to say facets in the zone of the tilt axis. Moreover, such a GB structure may affect the interpretation of recent phase sensitive experiments done on bicrystal or tricrystal high T{sub c} superconductors to determine the symmetry of the order parameter. {copyright} {ital 1998 American Institute of Physics.}
ISSN 00218979
Educational Use Research
Learning Resource Type Article
Publisher Date 1998-11-01
Publisher Place United States
Journal Journal of Applied Physics
Volume Number 84
Issue Number 9


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