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Electronic structure of BaO/W cathode surfacesThe local electronic structure of the emissive layer of barium dispenser thermionic cathodes is investigated theoretically using the relativistic scattered-wave approach. The interaction of Ba and O with W, Os, and W-Os alloy surfaces is studied with atomic clusters modeling different absorption environments representative of B- and M-type cathodes. Ba is found to be strongly oxidized, while O and the metal substrate are in a reduced chemical state. The presence of O enhances the surface dipole and Ba binding energy relative to Ba on W. Model results for W-Os alloy substrates show only relatively small changes in Ba and O for identical geometries, but very large charge redistributions inside the substrate, which are attributed to the electronegativity difference between Os and W. If Os is present in the surface layer, the charge transfer from Ba to the substrate and the Ba binding energy increase relative to W. Explanations are offered for the improved electron emission from alloy surfaces and the different emission enhancement for different alloy substrates.
Document ID
19890039491
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Muller, Wolfgang
(Analatom, Inc. Westlake, OH, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1989
Publication Information
Publication: IEEE Transactions on Electron Devices
Volume: 36
ISSN: 0018-9383
Subject Category
Electronics And Electrical Engineering
Accession Number
89A26862
Funding Number(s)
CONTRACT_GRANT: NAS3-24744
CONTRACT_GRANT: NAS3-25085
Distribution Limits
Public
Copyright
Other

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