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Superconductivity in molybdenum/tantalum superlattices and yttrium-barium-copper-oxide thin films

Thesis/Dissertation ·
OSTI ID:5946949
The properties of sputter-deposited multilayered superconductors have been studied, including Mo/Ta metallic superlattices and thin films of YBa{sub 2}Cu{sub 3}O{sub 7-x}. The former have been prepared with the same integer number of atomic planes of Mo and Ta modulating the layered composition. In contrast to behavior observed in other metal-metal superlattices, Mo/Ta exhibits long range structural coherence and metallic resistivity behavior over the entire range of wavelengths down to the monolayer limit. The structural properties of these superlattices are used to explain an anomalous decrease in the c{sub 44} elastic stiffness constant previously observed in Mo/Ta for 20 {angstrom} {le} {Lambda} {le} 50 {angstrom}. Superconductivity measurements indicate universal {Tc} versus {rho} behavior in Mo/Ta, and tunneling results show that these superlattices are weakly-coupled BCS superconductors. The second part of this dissertation examines the properties of superconducting thin films of YBa{sub 2}Cu{sub 3}O{sub 7-x} prepared by dc triode sputtering from metallic targets of Y and Ba{sub 2}Cu{sub 3}. Post-depression annealing in O{sub 2} is necessary to form the superconducting oxide. Various substrates were used, including sapphire and MgO, both with and without buffer layers of Ag, and SrTiO{sub 3}. The buffer layers are used to decrease the interaction of the substrate with the film.
Research Organization:
Arizona Univ., Tucson, AZ (USA)
OSTI ID:
5946949
Country of Publication:
United States
Language:
English