ISSN:
1089-7550
Quelle:
AIP Digital Archive
Thema:
Physik
Notizen:
Investigation of the 110-K Bi2Sr2Ca2Cu3Ox phase formation in superconducting thin films of Bi-based cuprates is reported. The films were dc magnetron sputtered from single Bi(Pb)-Sr-Ca-Cu-O targets of various stoichiometries, and subsequently annealed in air at high temperatures. The influence of the initial Pb content, annealing conditions, as well as the substrate material on the growth of the 110-K phase was investigated. We found that the films, fully superconducting above 100 K could be reproducibly fabricated on various dielectric substrates from Pb-rich targets by optimizing annealing conditions for each initial Pb/Bi ratio. Heavy Pb doping considerably accelerated formation of the 110-K phase, reducing the film annealing time to less than 1 h. Films containing, according to the x-ray measurement, more than 90% of the 110-K phase were obtained on MgO substrates, after sputtering from the Bi2Pb2.5Sr2Ca2.15Cu3.3Ox target and annealing in air for 1 h at 870 °C. The films were c-axis oriented, with 4.5-K-wide superconducting transition, and zero resistivity at 106 K. Their critical current density was 2 × 102 A/cm2 at 90 K, and above 104 A/cm2 below 60 K. The growth of the 110-K phase on epitaxial substrates, such as CaNdAlO4 and SrTiO3, was considerably deteriorated, and the presence of the 80- and 10-K phases was detected. Nevertheless, the best films deposited on these substrates were fully superconducting at 104 K and exhibited critical current densities above 2 × 105 A/cm2 below 60 K−one order of magnitude greater than the films deposited on MgO. We associate the presence of low-Tc phases in the films grown on epitaxial substrates with the intrinsic mechanism of the 110-K phase growth during the high temperature annealing process.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.349299
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