Photoemission and scanning tunneling microscope studies of quantum well and metal layer structures
Mueller, Mark Andreas
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https://hdl.handle.net/2142/20095
Description
Title
Photoemission and scanning tunneling microscope studies of quantum well and metal layer structures
Author(s)
Mueller, Mark Andreas
Issue Date
1990
Doctoral Committee Chair(s)
Chiang, Tai-Chang
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Condensed Matter
Language
eng
Abstract
A number of different metal layer structures have been examined using angle-resolved photoemission and scanning tunneling microscopy. In the past, research pertaining to electronic properties of quantum wells, interfaces, and superlattices has been mostly confined to the realm of semiconductor physics. However, the experiments described in this thesis demonstrate that such metal structures can be successfully probed with angle-resolved photoemission, revealing interesting electronic properties of these systems and opening a new frontier in experimental solid state research.
Experiments were performed using the single layer Ag/Cu(111) and Ag/Si(111) systems, the double layer Cu/Ag/Cu(111) and Au/Ag/Cu(111) systems, and Ag-Au superlattices. Quantum well states and resonances were observed in Ag/Cu(111) photoemission spectra. In this experiment, different overlayer thicknesses were grown, and hundreds of spectra were recorded for various normal and off-normal emission angles. Analysis of the quantum state photoemission data enabled a determination of the Ag sp bulk band structure. The phase shifts of Ag-vacuum and Ag-Cu boundaries were obtained in an experiment utilizing the Cu/Ag/Cu(111) double layer system. With the growth of Cu on Ag/Cu(111), the evolution of the top Ag boundary from Ag-vacuum to Ag-Cu produced measurable quantum state shifts. In a Ag-Au superlattice photoemission experiment, minibands and the gaps between these minibands were observed. The Ag/Si(111) overlayer was examined with both photoemission and STM. While quantum states were observed with photoemission, STM images show Ag layer growth in the form of (111) (100-250A)$\sp2$ domains. An experiment involving another system, Ca/Si(111), was the first STM study of alkali metal deposition. Images reveal the location of Ca on Si(111)-(7 x 7) for low Ca coverages. At higher Ca coverages and moderate annealing temperatures, a silicide forms whose reconstruction is (2 x 1). With higher annealing temperatures, a (3 x 1) reconstruction is observed.
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