The effect of microstructure on the electrical properties of YBCO interface-engineered Josephson junctions

The microstructure of interface engineered ramp-edge Josephson junctions in YBCO has been studied by transmission electron microscopy (TEM). The junctions are distinctly different from the structures found in heterophase SNS junctions. This structural difference can be directly related to the improv...

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Bibliographic Details
Published in:Physica. C, Superconductivity Superconductivity, 1999-03, Vol.314 (1), p.36-42
Main Authors: Huang, Y., Merkle, K.L., Moeckly, B.H., Char, K.
Format: Article
Language:English
Subjects:
BARIUM OXIDES
COPPER OXIDES
CRYSTAL STRUCTURE
DEFECTS
ELECTRICAL PROPERTIES
ENGINEERING
EPITAXY
INTERFACES
JOSEPHSON JUNCTIONS
LAYERS
MATERIALS SCIENCE
MICROSTRUCTURE
PLASMA
STRAINS
THICKNESS
TRANSMISSION ELECTRON MICROSCOPY
Transmission electron microscopy (TEM)
YBCO layers
YTTRIUM OXIDES
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Summary:The microstructure of interface engineered ramp-edge Josephson junctions in YBCO has been studied by transmission electron microscopy (TEM). The junctions are distinctly different from the structures found in heterophase SNS junctions. This structural difference can be directly related to the improved electrical properties of interface engineered junctions. The plasma treatment used in the interface engineering method forms a continuous barrier layer of 2 to 3 nm in thickness, much thinner than the deposited heterophase layers in SNS junctions. The layer, which separates the two YBCO layers, is crystalline, but has a crystal structure different from YBCO. The main factors responsible for the improved junction properties and their good reproducibility are: small barrier thickness, small thickness variation, weak interfacial strain fields, flat and nearly defect-free barrier/YBCO interfaces and good epitaxy of the second YBCO layer with few defects. Possible mechanisms for the formation of the large junction resistance are discussed.
ISSN:0921-4534
1873-2143
DOI:10.1016/S0921-4534(99)00028-3