High Critical Current Densities in Nb3Sn Films with Engineered Microstructures — Artificial Pinning Microstructures
Films with layers of Nb, Cu, and Sn have been fabricated to simulate a Nb3Sn bronze-type process. These Nb3Sn films have produced critical current densities greater than 1 × 106 A/cm2 at 4.2 K and 7.5 T. Niobium films doped with Y, Sc, Dy, Al2O3, and Ti have been deposited with e-beam co-evaporation onto 75 mm diameter Si wafers with a 100 nm SiO2 buffer layer. The Nb layer was followed by a layer of Cu and a layer of Sn to complete the bronze-type process. The films with the highest Jc had about 8 vol. % Sc and about 18 vol. % Al2O3. Characterization of the microstructure by TEM shows that these high Jc films contained high density of inclusions about 5 nm in size and that the grain size of the Nb3Sn is about 20–25 nm for samples heat treated at 700°C for up to eight hours.
KeywordsCoefficient Ofthermal Expansion Critical Current Density Undoped Film High Critical Current Density Wafer Processing
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