Browsing by Author "Jones, Stephen David"

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    Development of the analyser module for the MIDAS Data Acquisition System operating on the K600 magnetic spectrometer at iThemba LABS, Cape Town
    (2008) Jones, Stephen David; Fearick, Roger
    The focal-plane detector package at iThemba LABS, Cape Town, is reviewed and a new analyser module is developed. The mathematical methods employed by the analyser are also reviewed and the final system is calibrated and tested against experimental data taken at iThemba LABS, Cape Town.
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    Tomographic reconstruction of the morphology of silicon nanoparticleclusters
    (2014) Jones, Stephen David; Härting, Margit; Britton, David T
    Semiconducting silicon nanoparticles and nanoparticle clusters are studied using conventional TEM, high resolution TEM and transmission electron tomography techniques. TEM and TEM based tomography provide the means to determine the size and morphology of primary particles and clusters, while the structure of printed macroscopic layers has previously been characterised via small angle X-ray scattering (SAXS). High resolution TEM studies were also carried out on the nanoparticles at high magnification in order to examine the internal structure of the nanoparticles, which is found to contain both ordered as well as amorphous regions. As the nanoparticle clusters studied in this work are tightly bound, dense structures, traditional alignment techniques do not produce satisfactory alignment of the micrographs from which the tomograms are reconstructed, resulting in reconstructions which possess significant artifacts. This limitation is overcome by the development of a new correlation based alignment technique which produces superior alignment when compared to previous techniques, especially in the case of dense samples. The resulting alignment has allowed for the reconstruction of tomograms from which morphological information of the nanoparticle clusters is inferred. The clusters are found to be tightly bound hierarchical clusters, consisting of a large central core surrounded by smaller particles, whose surfaces are faceted. The morphological information gained from the tomography studies has been combined with the macroscopic structure of the layers to infer the arrangement of the nanoparticle clusters within the particle network of the printed layers.