Properties of epitaxial YBa sub 2 Cu sub 3 O sub 7-. delta. -based superconducting superlattices

Conference · Sun Sep 01 00:00:00 EDT 1991

OSTI ID:5337027

Norton, D P; Lowndes, D H; Zheng, Z Y; Feenstra, R ^[1]; Zhu, Shen ^[2]

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1. Oak Ridge National Lab., TN (United States)
2. Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy

Epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting superlattices have been fabricated using pulsed laser deposition in which c-axis oriented YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers as thin as one unit cell thick are separated by relatively thick PrBa{sub 2}Cu{sub 3}O{sub 7-{delta}} based barrier layers. The superlattice {Tc} (R=0) decreases rapidly with increasing barrier layer thickness, but then saturates at a finite {Tc} for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers as thin as a single c-axis unit cell. The superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7-{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, {Tc} (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-{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-{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-{delta}} layers in these superlattices. These steps may act as superconducting weak links, providing support for 2D Josephson-coupled-array models of superconducting superlattices. 34 refs., 5 figs.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5337027
• Report Number(s): CONF-9109102-1; ON: DE92000423
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HIGH-TC SUPERCONDUCTORS
MICROSCOPY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM OXIDES
RARE EARTH COMPOUNDS
SUPERCONDUCTIVITY
SUPERCONDUCTORS
SUPERLATTICES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES