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1998 HansenPDF


Title:Surface and interface effects in valence band photoemission of noble metals
Author(s):Hansen, Evan D.
Director of Research:Chiang, Tai-Chang
Department / Program:Physics
Subject(s):Noble metals
Valence Band Photoemission
Abstract:Angle-resolved photoemission probes sample initial and final states involved in direct transitions within the valence bands of the noble metals. Experiments studying these direct transitions have yielded fundamental understanding of the electronic structure of noble metals and of the valence band photoemission process. Recently, however, it has become apparent that the standard valence band photoemission treatment of the noble metals has not satisfactorily explained available data. At the same time photoemission experiments have made it increasingly obvious that interfaces can dramatically change the electronic structure of noble metal thin films. This thesis addresses the effects of the surface and interfaces on electronic structure and on the photoemission process in the noble metals copper and silver. One section of this thesis addresses the surface and interface effects on the electronic structure of the noble metal copper on different single crystal cobalt substrates. Careful comparison of the photoemission data with the band structure of the metals shows that the interface can be transparent or barrier-like depending on the valence band electronic structure. If the interface is transparent, the electronic structure of a copper film is very similar to that of bulk copper. If the interface is not transparent the surface and interface provide a confinement potential which results in quantum well states not found in bulk copper. Another section presents the solution to a long standing question about the asymmetric line shape of inter-band transitions in the noble metals. The asymmetry of this direct transition peak is a result of the involvement of the surface in the photoemission process. This is known as the surface photoemission effect. The change in dielectric function at the surface affects the photon field such that there are two resultant contributions to the line shape which interfere to produced the observed asymmetry. The third and final effect discussed in this thesis is also related to the line shape of the noble metal direct transition peak. The width of this peak is determined by the band structure and the orientation of the surface with respect to the propagation direction of the state of interest. Transitions from bands which are non-dispersive along the direction of the surface normal are found to have no contribution from the final state. Resultant direct transition peaks from silver are in fact narrower than the inverse lifetime limit.
Issue Date:1998
Genre:Dissertation / Thesis
Rights Information:© 1998 Evan D. Hansen
Date Available in IDEALS:2012-05-08
Identifier in Online Catalog:4162290

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