Doctoral Dissertations

Suichu Luo

Date of Award

5-1994

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

David C. Joy

Committee Members

R.H. Ritchie, J. J. Quinn, P. Liaw

Abstract

In the last four decades a variety of microscopes have been developed. Now the electron microscopes have well been established and become one of the most important tools to investigate the fundamental properties of electron-specimen interactions. When an electron beam irradiates a specimen, the resulting elastic scattering process canbe used to form images and diffraction patterns in the TEM, while the inelastic scattering induces secondary emissions, such as secondary electrons. Auger electrons and X-rays, which are the signals in the SBM, TEM, and STEM. EELS, an important analytical technique, which can be carried out only in the TEM or STEM, provides a direct access to the full information resulted from elastic and inelastic mixed scattering processes in the electron-specimen interactions. This thesis is concentrated on understanding the physical processes for signal generation in microanalysis. For SEM we have developed a detailed quantitative model to describe the production and escape of SE. For Monte Carlo simulation, a modified Rutherford formula has been proposed in order to obtain a satisfactory accuracy and more convenient computer procedure. For EELS, a new method to remove plural scattering and determine the local thickness of a specimen has been developed. This thesis also develops and applies an experimental method for the determination of stopping power in the low and medium energy range . The ionization of atoms by electrons is an important process in microanalysis. In this thesis we present the calculations of ionization cross sections of K , L and M shells covering the entire periodic table and sparming the energy range from the critical ionization energy up to 100 keV using Hartree-Slater self- consistent field model. In order to provide convenient access to this data some empirical formulae are derived, providing good quality fits to the computed results.

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