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Transmission Electron Tomography: Imaging Nanostructures in 3D Open Access


Other title
3D Reconstruction
Electron tomography
Transmission electron microscopy
Type of item
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 of Physics

Date accepted
Graduation date
Doctor of Philosophy
Degree level
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.
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