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Title: Super Resolution Tilt Series Exit Wave Restoration from Aberration Corrected Images
Author: Haigh, Sarah Jane
ISNI:       0000 0001 3524 0926
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2007
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Conventionally, the resolution of a transmission electron microscope is limited to the axial information limit. Higher resolution information may be transferred by tilting the incident illumination, which shifts the region of Fourier space that contributes to the image. This super resolution is highly directional, but may be extended in all directions by restoring the exit wave from images with a complimentary set of beam tilts. Although this may be achieved using a conventional microscope, an instrument where the primary aberrations are corrected electron optically provides significant advantages. This thesis explores the optimal conditions for achieving super resolution using the technique of tilt series restoration from aberration corrected images. The results demonstrate that for a tilt defocus data set of aberration corrected images acquired using the JEOL 2200FS 200 kV transmission electron microscope, the tilt induced changes in the coherent and incoherent aberrations limits the optimal tilt magnitude to 25 mrad or 19 mrad respectively. However, the optimal tilt magnitude will in most cases be limited to approximately 16 mrad by the thickness of the sample itself due to geometric parallax. The need for fundamental microscope stability and an appropriate detector set up is also discussed. Experimental exit wavefunction restorations from tilt defocus data sets of aberration corrected images are then presented for three specimens; <111> oriented strontium titanate, <123:> oriented gold and <112> oriented silicon. These restorations are compared to restorations using a standard focal series data set acquired immediately subsequent to the tilt defocus series. These results demonstrate that by the inclusion of tilted images in the exit wavefunction restoration data set an improvement in the continuous information transfer from 0.11 nm to 0.071 nm can be achieved at 200 kV.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available