Study on grain boundary Josephson junctions in BaPb/sub 1-x/Bi/sub x/O/sub 3/ thin films
Several characteristics have been experimentally investigated for the grain boundary Josephson junctions inherently formed at every grain boundary of polycrystalline sputtered BaPb/sub 1-x/Bi/sub x/O/sub 3/ superconducting thin films, where x = 0.2, 0.25, and 0.3. The origin of the boundary Josephson junction barrier is ascribed to the low carrier density, the structure sensitiveness, and surface states originating from the Bi ions in the grain boundary region, all of which this superconducting oxide posesses at the same time. The grain boundary Josephson junction exhibits tunneling-type I-V characteristics, which progressively change to those of a weak link in the temperature range near the superconducting transition temperature. The gap voltage observed is less than the value given by the Bardeen--Cooper--Schrieffer theory, except for x = 0.3. The temperature dependence of the maximum Josephson current deviates from the Ambegaokar--Baratoff theory in the same temperature range. All these tendencies are interpreted in terms of the McMillan tunneling model for a proximity sandwich, based on a model of a parabolic grain boundary potential barrier. Qualitative agreements are attained for the composition dependence of these characteristics. Relations between the Bi content and the junction barrier properties are also discussed, partly in relation to the strong coupling tendency in this oxide system.
- Research Organization:
- Ibaraki Electrical Communication Laboratory, Nippon Telegraph and Telephone Public Corporation, 162 Tokai, Ibaraki, 319-11 Japan
- OSTI ID:
- 6560989
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 56:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
BARIUM OXIDES
GRAIN BOUNDARIES
JOSEPHSON JUNCTIONS
BISMUTH OXIDES
TUNNEL EFFECT
LEAD OXIDES
SUPERCONDUCTING FILMS
ELECTRIC CONDUCTIVITY
ELECTRIC POTENTIAL
POLYCRYSTALS
SURFACES
TEMPERATURE EFFECTS
THIN FILMS
TRANSITION TEMPERATURE
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BISMUTH COMPOUNDS
CHALCOGENIDES
CRYSTAL STRUCTURE
CRYSTALS
ELECTRICAL PROPERTIES
FILMS
JUNCTIONS
LEAD COMPOUNDS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SUPERCONDUCTING JUNCTIONS
THERMODYNAMIC PROPERTIES
420201* - Engineering- Cryogenic Equipment & Devices