Photoemission and photoelectron diffraction studies of semiconductor surfaces
Sieger, Matthew Thomas
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https://hdl.handle.net/2142/22503
Description
Title
Photoemission and photoelectron diffraction studies of semiconductor surfaces
Author(s)
Sieger, Matthew Thomas
Issue Date
1996
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
Several experimental surface science techniques, such as photoelectron diffraction (PED), photoemission extended fine structure (PEFS), and photoelectron holography (PEH), rely upon the measurement of the interference due to the photoelectron wave scattering from nearby atoms. The intensity oscillations in the data are analyzed by comparison to theoretical models (PED), direct inversion to yield bond lengths (PEFS), or direct inversion to obtain a three-dimensional image (PEH). This thesis describes several experiments in which high-resolution photoemission spectroscopy, PEFS, and PEH have been employed to study the atomic structure of semiconductor surfaces.
The surface structure of GaSb(100) has been investigated using core-level photoemission spectroscopy. Quantum-mechanical diffraction effects are shown to have a significant effect on the measured photoemission spectra, seriously complicating analysis with the classical layer attenuation model. By accounting for photoelectron diffraction, our analysis overcomes these complications and gives a more accurate determination of surface stoichiometry than traditional methods.
One outstanding issue in the study of surface structure is the origin of surface shifts in core-level photoemission spectra. This problem has important consequences regarding our understanding of the physics of surface charge transfer, final state screening, and core level shifts. The inversion of PEH data gathered on a Ge(111)-c(2 x 8) surface core-level shift has produced three-dimensional images identifying the surface site responsible for the shift.
A study of the Sb core level for the Sb/Si(111) system shows that diffraction information can be derived from the intensity ratio (branching ratio) of the two spin-orbit-split peaks of a core level. Branching ratio fine structure spectroscopy provides an alternative and much simpler route to structural analyses than traditional cross section measurements, and the results are likely to be more accurate.
Finally, we have measured the photoelectron diffraction from the interfacial oxidation states of SiO$\sb2$/Si(111) and SiO$\sb2$/Si(100). Analysis of the photoemission extended fine structure gives bond-length information specific to the individual suboxides. The results indicate that a simple abrupt interface model fits the observed Si(111) data well.
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