Electron spectrometry, scope

The aim of this talk is to review the results obtained in the studies of inner-shell ionization and decay by means of photoelectron (PES) and Auger electron spectrometry (AES). Since the scope of such a talk would be much too broad I will consider AES only in connection with photon or electron impact ionization. AES associated with ion-atom collisions, important for studies of multi-ionized atoms, will not be discussed. The angular anisotropy of photo- and Auger electrons will also not be treated in spite of the fact that for inner-shells the B-para-meter may depend sensitively on the structure and the dynamics of the atom, in particular for heavier atoms (e.g. Xe(4d) > ). Therefore my talk will be more selective than exhaustive. By means of selected examples of inner-shell photo and Auger electron spectra I will demonstrate the sort of information one can obtain for atoms. The main emphasis will be laid on effects caused by the electron correlation. Reviews on parts of this subject have been given earlier by Siegbahn et al. Krause >, Mehlhorn , Wendin and most recently by Siegbahn and Karlsson ... 

Knowledge of the stracture and bonding of molecnles to snrfaces has been obtained from such techniques as LEED, electron energy-loss spectroscopy (EELS), secondaiy-ion mass spectrometry (SIMS), infrared spectroscopy (IRS), Raman spectroscopy, and NMR spectrometiy. The scope of snch studies needs to be greatly expanded to include the effects of coadsorbates, promoters, and poisons. Greater emphasis should be given to developing new photon spectroscopies that would permit observation of adsorbed species in the presence of a gas... 

The closely allied topics of secondary neutral mass spectrometry (SNMS), fast atom bombardment (FAB), and laser ablation SIMS are important, but are beyond the scope of this chapter. SNMS is a technique in which neutral atoms or molecules, sputtered by an ion beam, are ionized in an effort to improve sensitivity and to decouple ion formation from matrix chemical properties, making quantification easier. This ionization is commonly effected by electron beams or lasers. FAB uses a neutral atom beam to create ions on the surface. It is often useful for insulator analysis. Laser ablation creates ions in either resonant or nonresonant modes and can be quite sensitive and complex. 

Plasma diagnostics consists of tools that can be used to characterize the plasma and thus provide information on the processes that are occurring with the plasma etcher. The main tools employed are spectroscopy, emission spectroscopy, mass spectrometry, and plasma probes. A detailed discussion on how each tool works is beyond the scope of this review. However, these tools are used to identify the species present in the plasma etcher, determine the temperature of the species, and determine the electron density. 

When it comes to the important but difficult issues of scope and limitations, there is one clear-cut borderline. The Handbook covers wet but not dry surface chemistry. This means that important applications of dry surface chemistry, such as heterogeneous catalysis involving gases, and important vacuum analysis techniques, such as Electron Spectroscopy for Chemical Analysis (ESCA) and Selected-Ion Mass Spectrometry (SIMS), are not included. Within the domain of wet surface chemistry, on the other hand, the aim has been to have the most important applications, phenomena and analytical techniques included. 

The student should be aware that there is another class of surface analysis instruments based on analytical microscopy, including scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and scanning tunneling microscopy. A discussion of these microscopy techniques is beyond the scope of this chapter. Most industrial materials characterization laboratories will have some combination of electron spectroscopy. X-ray analysis, surface mass spectrometry, and analytical microscopy instrumentation available, depending on the needs of the industry. 

High-resolution Auger or secondary ion mass spectrometry (SIMS) analyses of see fracture surfaces, especially around crack-arrest features, have not kept pace with instrument development, and there is great scope for well-designed experiments of this type supported by cross-sectional transmission electron microscopy. 

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