ELECTRONIC STRUCTURE AND CHEMICAL ACTIVITY OF MODIFIED METAL SURFACES (PHOTOEMISSION, THIN FILMS, CHEMISORPTION).
Item
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Title
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ELECTRONIC STRUCTURE AND CHEMICAL ACTIVITY OF MODIFIED METAL SURFACES (PHOTOEMISSION, THIN FILMS, CHEMISORPTION).
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Identifier
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AAI8708313
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identifier
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8708313
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Creator
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PAN, XIAOHE.
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Contributor
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Myron Strongin
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Date
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1987
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Condensed Matter
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Abstract
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Angle-resolved synchrotron radiation photoemission has been used, together with k-resolved inverse photoemission, low-energy electron diffraction, and Auger electron spectroscopy, to study the occupied and unoccupied electronic states, the morphology, and the chemical activity of Ni, Pd, and Pt overlayers on Nb(110) and Ta(110) substrates.;The strong adlayer-substrate bonding leads to the formation of highly strained commensurate Pd and Pt layers in the early growth stage. However, Ni agglomerates and forms incommensurate structures because the additional lattice mismatch cannot be overcome by the adsorbate-substrate bonding. In the photoemission studies of these metal-metal systems, the adlayer derived bonding interface resonance is observed at a higher binding energy part of the d- band below the Fermi level (E(,F)). The dominance of this bonding interface resonance and the absence of d- states near E(,F) makes the valence band electronic structure of Pt and Pd monolayer noble-metal-like. Chemisorption studies at 300 K show that CO does not chemisorb on the surface of a monolayer of Pt or Pd on Nb(110). However, both dissociative and molecular CO adsorption occurs on Nb(110) covered by a equivalent monolayer of Ni.;K-resolved inverse photoemission identifies an antibonding interface resonance at 1.6 eV above E(,F) for a monolayer of Pd on Nb(110). This mainly Nb-derived interface state is confirmed by the dispersion of two-dimensional band structure along the surface normal and surface Brillouin zone. The experiments further show that the interface bond weakens as the thickness of the overlayers increases. Together with the photoemission results, a further insight into the physical and chemical properties of these transition metal-metal systems can be achieved by a simple picture of d-d hybridization between the adlayer and substrate with a bonding level below E(,F) and an antibonding level above E(,F).
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Physics
