toward understanding dynamic annealing processes in irradiated ceramics

187 Pages·2013·2.99 MB·English

LLNL-TH-611672
TOWARD UNDERSTANDING
DYNAMIC ANNEALING
PROCESSES IN IRRADIATED
CERAMICS
M. T. Myers
January 18, 2013
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This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore
National Laboratory under Contract DE-AC52-07NA27344.
Rev. 1.2
TOWARD UNDERSTANDING DYNAMIC ANNEALING PROCESSES IN
IRRADIATED CERAMICS
A Dissertation
by
MICHAEL THOMAS MYERS
Submitted to the Office of Graduate Studies of
Texas A&M University
in partial fulfillment of the requirements for the degree of
DOCTOR OF PHILOSOPHY
Approved by:
Chair of Committee, Lin Shao
Committee Members, Sergei Kucheyev
Sean McDeavitt
Haiyan Wang
Xinghang Zhang
Department Head, Yassin Hassan
May 2013
Major Subject: Nuclear Engineering
Copyright 2013 Michael Thomas Myers
Rev. 1.2
ABSTRACT
High energy particle irradiation inevitably generates defects in solids. The bal-
listic formation and thermalization of the defect creation process occur rapidly, and
are believed to be reasonably well understood. However, knowledge of the evolution
of defects after damage cascade thermalization, referred to as dynamic annealing,
is quite limited. Unraveling the mechanisms associated with dynamic annealing is
crucial since such processes play an important role in the formation of stable post-
irradiation disorder in ion-beam-processing of semiconductors, and determines the
“radiation tolerance” of many nuclear materials. The purpose of this dissertation
is to further our understanding of the processes involved in dynamic annealing. In
order to achieve this, two main tasks are undertaken.
First, the effects of dynamic annealing are investigated in ZnO, a technologically
relevant material that exhibits very high dynamic defect annealing at room temper-
ature. Such high dynamic annealing lead to unusual defect accumulation in heavy
ion bombarded ZnO. Through our work, the puzzling features that were observed
more than a decade ago in ion-channeling spectra have finally been explained. We
show that the presence of a polar surface substantially alters damage accumulation.
Non-polar surface terminations of ZnO are shown to exhibit enhanced dynamic an-
nealing compared to polar surface terminated ZnO. Additionally, we demonstrate
one method to reduce radiation damage in polar surface terminated ZnO by means
of a surface modification. These results should further our efforts in the long-sought-
after goalofunderstanding complex radiationdamageprocesses innon-amorphizable
oxides.
Second, a pulsed ion beam method is developed and implement using Si as a
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Rev. 1.2
prototypical ceramic target. Such a method is shown to provide a novel experimen-
tal method for direct extraction of dynamic annealing parameters. The relaxation
times and effective diffusion lengths of mobile defects during the dynamic anneal-
ing process play a vital role in damage accumulation. We demonstrate that these
parameters dominate the formation of stable post-irradiation disorder. In Si, a de-
fect lifetime of 6 ms and a characteristic defect dffiusion length of 30 nm are
∼ ∼
measured. These results should nucleate a number of future pulsed-beam studies of
dynamic defect interaction processes in technologically relevant materials. In partic-
ular, understanding the length and time scales of defect interactions are essential for
extending laboratory findings to nuclear material lifetimes and to the time scales of
geological storage of nuclear waste.
The results of both, the pulsed beam method for measuring dynamic annealing
parameters, as well as damage accumulation in various planes of ZnO bombarded by
heavy ions, are discussed. The work presented in this dissertation should substan-
tially further our understanding of dynamic annealing processes in ceramics.
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Rev. 1.2
DEDICATION
To my wife and my parents, thank you for your endless encouragement.
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Rev. 1.2
ACKNOWLEDGEMENTS
Iwouldliketoacknowledge Dr.Shaoforhisguidancesupportduringmytenureat
Texas A&M University. I would like to thank my committee members, Dr. McDeav-
itt, Dr. Wang, and Dr. Zhang for their support over the course of the present work.
An additional debt of gratitude is owed to my Lawrence Livermore National Labora-
torymentor, Dr.Kucheyev, whospent countless hourshelping megrowintoamature
scientist. A sincere “thank you” to Dr. Charnvanichborikarn who spent many hours
assisting with experimental design as well as performing the actual experiments at
Lawrence Livermore National Laboratory. I would also like to thank my group mem-
bers, colleagues, and collaborators, Dr. Aitkaliveya, Dr. Luo, Dr. Lee, M. S. Martin,
D. Chen, M. Hollander, C. C. Wei, M. A. Myers, J. Wallace, and M. J. General for
their help throughout the dissertation.
Finally,IwouldliketoacknowledgetheLawrenceScholarProgramattheLawrence
Livermore National Laboratory for funding the work performed in this dissertation.
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Rev. 1.2
NOMENCLATURE
A Ampere
Al O Aluminum Oxide
2 3
AlO(OH) Aluminum Oxide Hydroxide
BF Bright Field
BP Bulk Defect Peak
C Coulomb
CdTe Cadmium Telluride
CM Center of Mass
DA Dynamic Annealing
DF Dark Field
DLTS Deep Level Transient Spectroscopy
DPA Displacement Per Atom
EDS Energy Dispersive X-ray Spectroscopy
eV Electron Volt
FIB Focused Ion Beam
FZ Float Zone
HAADF High Angle Annular Dark Field
HEIS High Energy Ion Scattering
IBA Ion Beam Analysis
IBM Ion Beam Modification
IED Ionization Enhanced Diffusion
IP Intermediate Defect Peak
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Rev. 1.2
keV Kilo Electron Volt
KP Kinchin-Pease
L Diffusion Length
d
LED Light Emitting Diode
LLNL Lawrence Livermore National Laboratory
MeV Mega Electron Volt
ME Molecular Effect
MD Molecular Dynamics
MgO Magnesium Oxide
MgAl O Magnesium Aluminate Spinel
2 4
NEC National Electrostatics Corporation
nm Nanometer
NRT Norgett, Robinson and Torrens
PKA Primary Knock-on Atom
PL Photoluminescence
RBS/C Rutherford Backscattering and Channeling Spectrometry
RT Room Temperature
Si Silicon
SiC Silicon Carbide
Si N Silicon Nitride
3 4
SP Surface Defect Peak
SPER Solid Phase Epitaxial Recrystallization
SRIM Stopping and Range of Ions in Matter
SRP Spreading Resistance Profiling
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Rev. 1.2
STEM Scanning Transmission Electron Microscopy
Tau (τ) Defect Lifetime
TEM Transmission Electron Microscopy
TFD Thomas-Fermi-Dirac
TRIM Transport and Range of Ions in Matter
UN Uranium Nitride
UO Uranium Oxide
2
XTEM Cross Sectional Transmission Electron Microscopy
ZnO Zinc Oxide
viii