Monte Carlo Simulation Of Auger Electron Emission From Thin Film On Substrate

A thin film substrate is a layer of material applied with thin film technology. Many industrial and technological devices require coating with a thin layer of a particular chemical substance. Thin film materials are widely used in solar cells, computer hard-ware, and batteries to make the most efficient use of materials. The film thickness plays an important role in coating techniques. Therefore, a technique, suitable for many im-portant substrates, for determining thickness of thin films is needed because of the rapid development of this field, and, because the unique properties of film/substrate systems are strongly dependent on the thickness and interaction with the underlying substrate.Auger electron spectroscopy (AES) is a standard and powerful surface analytical technique. AES spectrum usually provides information on the outermost surface layers of the material because Auger electrons formed only in the very near surface of the material are likely to escape and be detected without energy loss. The work is aiming to simulate the effects of films on the Auger energy spectrum of the substrate by Monte Carlo method with up-to-date scattering theory of electrons and solid atoms. We use the Auger peak intensity of the substrate to characterize the thickness of the uniform film on the substrate, and obtain the general relationship between the Auger signal intensity and the film thickness and derive the relevant effective attenuation length. The following describes the specific content of the thesis.In Chapter 1, we introduced the basic principles of Auger electrons and Auger spec-troscopy applications, and Auger electron spectroscopy has been successfully applied to many scientific fields. Then we introduce several commonly used physical quanti-ties in the electron spectroscopy experiments of thin film substrate materials: inelastic mean free path and effective attenuation length. We also introduce the application of the scattering theory of electron-solid interaction in quantitative Auger analysis.In Chapter 2, we describe in detail the elastic and inelastic scattering theory of electron-solid interaction, as well as the principle of inner shell excitation and Auger electron production. In this thesis, the simulation is based on the uses of Mott’ s elastic scattering cross section and Penn’ s dielectric function approach to electron inelastic scattering. The cascade secondary electron production and Auger electron generation in inner-shell ionizations events are described by the Gryzinski’ s ionization cross section.In Chapter 3, we first introduce the important application of Monte Carlo method in scientific research, and the advantages of Monte Carlo method to deal with complex problems. Then, based on the scattering theory in Chapter 2, we introduce the Monte Carlo method in simulating the transport of electrons in solid, and give a flow chart of the simulation program.In Chapter 4, we perform the Monte Carlo simulation of the Auger electron spec-trum for film/subtrate specimens (Al on Ag and Ag on Cu) by including both elastic and inelastic scattering. Bulk plasmon excitation peaks from both film and substrate are found in the low loss region near the elastic peak and the AES signal peak. The cal-culated Auger electron spectrum was subtracted for background, leading to obtain the approximate exponential decay behavior of Auger signal intensity with the film thick-ness. We discuss the film thickness measurement by characterizing the decay curve and effective attenuation length, leading to define two attenuation parameters to character-ize the decay functional shape used as the calibration curve for accurate film thickness determination.In Chapter 5, we summarize this thesis, look forward to the prospect and applica-tion of the work.