Angle resolved photoemission studies of silver bromide
Kwawer, Gary Neil
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https://hdl.handle.net/2142/23937
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
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
angle resolved photoemission
polarized synchrotron radiation
Silver Bromide (AgBr)
AgBrI
Language
en
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 ~-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 AgBrl halogen PDOS extended 0.2e V 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 r 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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