Aspects of a theoretical and computational basis for the simulation of fast electron scattering in a solid due to elastic, electron-phonon and atomic ionisation events are developed. The primary motivation for this work arises from the need for detailed simulations of fast electron scattering to assist in the quantitative interpretation of experimental data acquired using high-spatial-resolution analytical techniques in the scanning transmission electron microscope. The scattering behaviour of Å-scale electron probes in simple atomic structures is examined with specific reference to the origin of core energy-loss signals and the spatial resolution of annular dark-field images generated by such probes. A multiscale theory of the dynamical elastic and inelastic scattering of fast electrons is then developed. This theory is applicable to many forms of inelastic scattering, and is developed in the form of a multi-dimensional extension of the well-known multislice theory of dynamical elastic scattering of fast electrons. Methods for obtaining the key quantities required for the application of this theory to the inelastic scattering of fast electrons due to atomic ionisation are presented. One of these methods is extended to enable the inclusion of relativistic effects in the ionisation process. A preliminary test of the multislice theory is made by comparing calculated and experimental characteristic-loss electron diffraction patterns acquired from silicon. The treatment of incoherent electron waves using Monte Carlo integration, which in certain circumstances can reduce computation time dramatically, is also demonstrated. Finally, the predictions of the theory are compared with those of approximate methods for calculating the origin of the core energy-loss signal in the scanning transmission electron microscope.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:598710 |
| Date | January 2004 |
| Creators | Dwyer, C. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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