Tungsten tip and atomic site tomography

Poon, Ho Yee Timothy (2020). Tungsten tip and atomic site tomography. University of Birmingham. Ph.D.

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Abstract

Atomic electron tomography aims to precisely locate individual atoms of a nanoparticle in three-dimensional space. In this work, a tomography method based on tungsten tips is developed to allow images to be taken over a full angular range by placing a nanoparticle on the apex of an etched tungsten tip. There is no interference of signal from supporting materials with the suspended nanoparticle. A new reconstruction algorithm, atomic site tomography, is developed using the principle of regularisation in multiple linear regression. This algorithm is specifically designed for identifying the precise locations of individual atoms in three-dimensional space, and the algorithm is validated by an experimental dataset. A gold nanoparticle dataset is successfully obtained by tungsten tip tomography, and the dataset is processed to remove scanning artefacts. Selected region of the gold nanoparticle dataset is used to demonstrate the new reconstruction algorithm and the whole gold nanoparticle is then reconstructed. A tuning fork atomic force microscope is developed to provide a more flexible method to prepare samples for tungsten tip tomography and its progress is reported. This work contributes to the field of atomic electron tomography by improving the experimental techniques for acquiring high-quality tomography dataset and proposing a new reconstruction algorithm which aims at locating individual atoms of nanoparticles precisely.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):