Superconducting properties and microstructure of YBa sub 2 Cu sub 3 O sub 7-. delta. /PrBa sub 2 Cu sub 3 O sub 7-. delta. superlattices

Conference · Tue Oct 01 04:00:00 EDT 1991

OSTI ID:6113047

Lowndes, D H; Norton, D P; Zheng, X Y ^[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}}/PrBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO/PBCO) superlattices are tools for systematic, fundamental studies of high-temperature superconductivity. The variation of {Tc} in YBCO/PBCO superlattices can be understood as arising from changes in the interlayer phase coupling between YBCO layers that are highly two-dimensional when they are very thin ({approximately}1--2 c-axis unit cells) and completely isolated from each other. Single-cell-thick YBCO layers, containing isolated pairs of CuO{sub 2} planes, are found to be superconducting at {Tc} {approximately} 20 K, in a PBCO matrix. The resistance in the superconducting transition region scales with temperature as expected for the (flux flow) resistance produced by thermally generated 2D vortices, or for a 2D array of superconducting weak links. Relative to both thin-film and single-crystal HTSc specimens, the thin superconducting layers in YBCO/PBCO superlattices exhibit a greatly expanded temperature range over which characteristic 2D dissipation can be observed, as a consequence of the enhanced anisotropy and reduced dimensionality of the YBCO layers. Scanning tunneling microscope studies reveal that YBCO films and YBCO/PBCO superlattices grow unit cell-by-unit cell by a terraced-island growth mechanism. On miscut, near-(001) substrates the terraces are epitaxially aligned with the substrate crystal lattice and spiral growth structures (screw dislocation-mediated growth) are not seen. These observations explain the steps or kinks'' that are seen in cross-section Z-contrast TEM images of YBCO/PBCO superlattices. The kinks may correspond physically to regions where the supercurrent must tunnel along the c- axis, and thus may be weak-link barriers. 31 refs., 7 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: 6113047
• Report Number(s): CONF-911096-3; ON: DE92003512
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360207* -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
DIMENSIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HIGH-TC SUPERCONDUCTORS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM OXIDES
RARE EARTH COMPOUNDS
SUPERCONDUCTIVITY
SUPERCONDUCTORS
SUPERLATTICES
THERMODYNAMIC PROPERTIES
THICKNESS
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES