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Permanent link (DOI): https://doi.org/10.7939/R3VT65

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Transmission Electron Tomography: Imaging Nanostructures in 3D Open Access

Descriptions

Other title
Subject/Keyword
3D Reconstruction
Electron tomography
Nanostructure
Transmission electron microscopy
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Wang, Xiongyao
Supervisor and department
Malac, Marek (National Institute for Nanotechnology)
Meldrum, Al (Physics)
Examining committee member and department
Ivey, Douglas (Chemical and Materials Engineering)
Hegmann, Frank (Physics)
Braidy, Nadi (Chemical and Biotechnological Engineering)
McCreery, Richard (Chemistry)
Department
Department of Physics
Specialization

Date accepted
2012-07-23T11:53:35Z
Graduation date
2012-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
In studies of nanoscale materials, electron tomography (ET) can be used to obtain three dimensional information on the morphology and spatial distribution of nanoparticles. Electron tomography records a tilt series of projected images of an object and then mathematically reconstructs a 3D map of the object from the recorded images. Filtered back-projection (FBP), which is based on spatial Fourier transforms, and simultaneous iterative reconstruction techniques (SIRT), which are purely algebraic, are the two common reconstruction methods used to generate a tomographic "3D matrix" from the recorded images. Three aspects of ET were investigated in this thesis: the reconstruction and visualization, experimental considerations, and practical applications. First, to quantify the quality of the reconstruction and the selection of visualization threshold was discussed. The quality of the reconstruction by FBP and SIRT methods was evaluated by root mean square (RMS) difference frequency analysis, a quantitative description of similarity between the original test and its reconstruction. A quality index (QI) method was proposed and successfully applied to set the visualization threshold for volume rendering of tomographic reconstructions. Setting the threshold according to a priori known space-filling volume fraction of nanoparticles was found not to be a suitable parameter for visualization. The effect of the filter used in FBP was examined. On the experimental front of electron tomography, a new ET sample preparation method was developed. The new method combines standard thin film deposition techniques and focused ion beam (FIB) milling. The proposed method minimized the effect of the projected thickness and missing wedge by controlling the thickness of the thin film and the width of the bar. Furthermore, the new method reduces gallium implantation problems and is suitable for tomographic sample preparation of samples in solution. Finally, the tomographic results of latex nanoparticles, Au nanocrystal multilayer, and Si nanocrystals embedded in silica glass were examined. A new method was developed by combining high angle annular dark-field (HAADF) and energy-filtered STEM techniques simultaneously to obtain parallel recording of 3D tomographic data from two different types of nanoparticles. This method was successfully applied to investigate the Er doped Si nanocrystals system.
Language
English
DOI
doi:10.7939/R3VT65
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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