Photoemission Studies of Thin Metallic Overlayer Systems

Angle-resolved photoemission spectroscopy was used to study Ag(111) monolayers on six different substrates: Ni(001), Ni(111), Cu(001), Cu(111), Au(111), and Si(111)-(7x7). The properties of surface states were also examined for several related systems: Cu(111) covered by various thicknesses of Ag, and a bare Cu(332) stepped surface. Monolayer overlayers that are incommensurate with the substrate Ag on Ni(001), Ni(111), and Cu(111) or commensurate with the substrate only over a large unit cell Ag on Cu(001) show electronic structures essentially independent of the substrate orientation and material, except for an overall shift in binding energy. The overlayer electronic structure is somewhat different for the Ag/Au(111) system, where there is a nearly perfect overlayer-substrate lattice match as well as substantial overlap in energy bands of like characters. In the Ag/Si system, partially disordered overlayer growth and a strongly corrugated substrate surface structure cause the overlayer features in the spectra to broaden substantially. For thicker Ag overlayers on Cu(111), the growth mode of the Ag was determined to be layer by layer despite the large mismatch between the two lattices. The Cu(111) surface state was observed to evolve monotonically for increasing Ag overlayer thickness to eventually become the Ag(111) surface state. The measured rate of shift of the surface state binding energy can be explained qualitatively in terms of the degree of localization of the surface-state wave functions. For the stepped Cu(332) surface, a feature believed to be an L-gap surface state is observed just below the Fermi edge in the photoemission spectra. The properties of this surface state are compared with known properties of the Cu(111) L-gap surface state.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Shapiro, Alan Paul

• Physics, Condensed Matter

Language dc:language

eng

Identifier

(UMI)AAI8711876

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/77404