Phase-selective route to high T sub c superconducting Tl sub 2 Ba sub 2 Ca sub n minus 1 Cu sub n O sub 2 n +4 films: Combined metalorganic chemical vapor deposition using an improved barium precursor and stoichiometry-controlled thallium vapor diffusion

Journal Article · Mon Jan 14 00:00:00 EST 1991 · Applied Physics Letters; (USA)

DOI:https://doi.org/10.1063/1.104966· OSTI ID:6258448

Malandrino, G; Richeson, D S; Marks, T J; DeGroot, D C; Schindler, J L; Kannewurf, C R ^[1]

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1. Science and Technology Center for Superconductivity and the Materials Research Center, Northwestern University, Evanston, Illinois 60208 (US)

Films of the Tl{sub 2}Ba{sub 2}Ca{sub {ital n}{minus}1}Cu{sub {ital n}}O{sub 2{ital n}+4} high {ital T}{sub {ital c}} superconductors ({ital n}=2 or 3) can be prepared with a high degree of phase selectivity using a combination of metalorganic chemical vapor deposition (MOCVD) and vapor diffusion. Ba-Ca-Cu-O films are first prepared by MOCVD using the volatile metalorganic precursors Ba(hexafluoroacetyl- acetonate){sub 2}(tetraglyme), Ca(dipivaloylmethanate){sub 2}, and Cu(acetylacetonate){sub 2}. The second-generation'' barium precursor exhibits significantly improved thermal stability and volatility over previously used compounds. Thallium is then incorporated into these films by vapor diffusion using a Tl-Ba-Ca-Cu oxide mixture of controlled composition as the source of volatile thallium oxides. Phase control is achieved by a combination of improved stoichiometry of the deposited film, a result of the new Ba source, and annealing with the appropriate oxide mixture. The resultant films consist predominantly of the Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub {ital x}} or Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub {ital x}} phase, each having preferential orientation of the crystallite Cu-O planes parallel to the substrate surface. The films exhibit superconducting onset temperatures of {similar to}115 K with zero resistance by 93 and 85 K, respectively. Critical current densities for a number of films, estimated by the Bean method, are in the range 10{sup 4}--10{sup 5} A/cm{sup 2} at 5 K.

• OSTI ID: 6258448
• Journal Information: Applied Physics Letters; (USA), Vol. 58:2; ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
CHEMICAL VAPOR DEPOSITION
SUPERCONDUCTIVITY
CALCIUM OXIDES
COPPER OXIDES
THALLIUM OXIDES
DIFFUSION
HIGH-TC SUPERCONDUCTORS
ORGANOMETALLIC COMPOUNDS
STOICHIOMETRY
SUPERCONDUCTING FILMS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL COATING
COPPER COMPOUNDS
DEPOSITION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
FILMS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SUPERCONDUCTORS
SURFACE COATING
THALLIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies