Author:
Chan Siu-Wai,Zhao Lie,Chen C.,Li Qi,Fenner D.B.
Abstract
Gold (Au) and silver (Ag) are known to be important contact metals on YBa2Cu3O7−x (YBCO). Both metals have been used as additives in fabricating tapes of YBCO and Bi2Sr2CaCu2O8 (BSCCO) materials, and have favorable results in improving not only the flexibility but also the weighted critical currents of the resulting composites. Previous results on superconductor/normal metal/superconductor junctions made using YBCO/Au/YBCO and YBCO/Au/Nb demonstrated that a supercurrent can be induced in the normal metal layers through the proximity effect. Our transmission electron microscopy study of the Au/YBCO interfaces shows a well-bonded interface with no extraneous phases present. Lattice fringes of the (001) plane in YBCO terminated at the interface abruptly. This observation supports previous results of contact resistance of x-ray photoelectron spectroscopy (XPS). Both (001) integral steps and multiples of 1/3 (001) steps were observed at the Au/YBCO interface. When the top gold layer was absent locally, surface degradation was observed as the (001) lattice fringes stopped short from the surface by 10 nm. Our results support that Au is a desirable contact metal and a dependable surface passivation material for YBCO.
Publisher
Springer Science and Business Media LLC
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics,General Materials Science
Reference16 articles.
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5. 16Contact resistivity1 of Au/YBCO interfaces from an ex situ process was reported to be 8.6 × 10–3 Ω cm2 at 300 K and 4.9 × 10–5 Ω cm2 at 77 K, while a lower value13 of 2.6 × 10–7 Ω cm2 at 79 K with oxygen anneal from an exsitu process and even a lower contact resistivity14 in the range of 10–8 – 10–9 Ω cm2 at 4 K from an in situ process without oxygen anneal had been reported.
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