Angle resolved photoemission studies of silver-bromide
Kwawer, Gary Neil
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https://hdl.handle.net/2142/21830
Description
Title
Angle resolved photoemission studies of silver-bromide
Author(s)
Kwawer, Gary Neil
Issue Date
1989
Doctoral Committee Chair(s)
Brown, Frederick C.
Department of Study
Chemical Physics
Discipline
Chemical 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
In this work, polarized synchrotron radiation is used to obtain both angle resolved photoemission data and angle integrated photoemission data on randomly oriented thick films of metallic silver, thin films of randomly oriented polycrystalline AgBr and AgBrI, and epitaxially grown AgBr on an Ag (111) single crystal.
The experiments on the randomly oriented samples were concerned with obtaining the correct sample preparation methods--evaporation of AgBr or AgBrI onto Ag which was evaporated onto an Au plated glass disc; the correct temperature conditions--sample temperature must be kept below 140K, preferably close to 77K, in order to stop sample photolysis and decrease electron-phonon interactions. Asymmetry parameters as well as relative cross sections were determined for the valence bands of Ag and AgBr from 55eV through the Ag 4d Cooper minimum at 140eV. Comparison of asymmetry parameters with atomic data indicates that the valence bands derived from the Ag 4d levels in these systems are remarkably atomic-like. In AgBr, only the uppermost valence bands show a greatly reduced excursion of $\beta$-value through the Cooper minimum.
The total and partial valence band density of states (DOS and PDOS) for AgBr and AgBrI were experimentally obtained. The Ag 4d PDOS was nearly identical for both compounds. The halogen derived PDOS's differed in that the AgBrI halogen PDOS extended 0.2eV closer to the vacuum level than its AgBr counterpart.
Experiments on AgBr epitaxially grown on Ag (111) single crystals demonstrated a definite surface core level shift (SCS) towards lower binding energy by 0.8eV for the Br 3d subshell. Unfortunately, these results do not conclusively state which ion terminates the surface. The general belief is that an AgBr (111) surface is bromide terminated.
Preliminary band mapping experiments were performed on epitaxially grown AgBr on an AgBr (111) single crystal from $\Gamma$ to L in the first Brillouin zone which experimentally located the valence band maximum at L. Comparing the experimentally obtained band structure with speculative ones shows that the experimental ones are flatter than their speculative counterparts.
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