Properties of epitaxial YBa sub 2 Cu sub 3 O sub 7 minus. delta. -based superconducting superlattices
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN 37996 (United States) Health and Safety Research Division, Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6056 (United States)
Epitaxial YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}-based superconducting superlattices have been fabricated using pulsed laser deposition in which {ital c}-axis oriented YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} layers as thin as one unit cell thick are separated by relatively thick PrBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}-based barrier layers. The superlattice {ital T}{sub {ital c}} ({ital R}=0) decreases rapidly with increasing barrier layer thickness, but then saturates at a finite {ital T}{sub {ital c}} for YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} layers as thin as a single {ital c}-axis unit cell The superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}-based superlattices are shown to depend strongly on the electronic properties of the barrier layers. The resistive transition width decreases significantly as the hole carrier density in the barrier layers is increased. However, {ital T}{sub {ital c}} (onset) does not change, contrary to predictions of hole filling models. Theoretical analyses suggest that the broadening of the resistive transition for the thinnest YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} layers is most likely due to a crossover to 2D resistive behavior involving thermally-generated vortices. Scanning tunneling microscopy reveals that epitaxial YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films grow unit cell-by unit cell, by a terraced-island growth mode. This terraced microstructure explains the steps found in ultrathin YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} layers in these superlattices. These steps may act as superconducting weak links, providing support for 2D Josephson-coupled-array models of superconducting superlattices.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5000137
- Report Number(s):
- CONF-9109102--
- Journal Information:
- AIP Conference Proceedings (American Institute of Physics); (United States), Journal Name: AIP Conference Proceedings (American Institute of Physics); (United States) Vol. 251:1; ISSN 0094-243X; ISSN APCPC
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360207* -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EPITAXY
HIGH-TC SUPERCONDUCTORS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SUPERCONDUCTORS
SUPERLATTICES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES