Growth and electronic properties of selected bimetallic interfaces.
Item
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Title
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Growth and electronic properties of selected bimetallic interfaces.
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Identifier
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AAI9108122
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identifier
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9108122
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Creator
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Jiang, Liqiang.
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Contributor
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Adviser: Myron Strongin
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Date
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1990
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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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The growth and electronic properties of selected bimetallic interfaces are studied using AES, LEED, LEIS and photoemission. A more systematic understanding of complex interfacial phenomena is obtained by simple models based on energetics. It is found that Rh agglomerates on Ta(110) but grows layer by layer on Mo(110) which has less lattice mismatch. A transition from the Kurdjumov-Sachs to the Nishiyama-Wassermann orientation is observed for the first time during the growth of Rh(111) monolayer on Mo(110). It is demonstrated that alloying may occur even at 300 K if the surface energy of the overlayer is higher than the substrate and the bonding of the metal pair is strong, as in the case of Pd/Al and Nb/Pd.;The direction of electronic charge transfer between an adatom and a metallic substrate is shown to be determined by the sign of J = (I + A)/2-{dollar}\phi{dollar}, where A and I are the affinity and ionization level of the adatom and {dollar}\phi{dollar} is the substrate work function. This criterion enables a unified understanding of the work function trends of the various systems studied in this thesis as well as other systems that have not been explained previously. Although both Nb and Pd surfaces readily adsorb CO, the alloy surface obtained by depositing 1 ML Nb on Pd is found to be inert to CO adsorption at 300 K. Further evidence is found for the strong correlation between the density of states near the Fermi level and CO adsorption, or more generally, catalytic properties of bimetallic systems. Together this work has led to deeper insight into interface formation and the crucial role of electronic structure in surface chemistry.
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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.
