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W.S.M. Werner:
"Electron Transport in Solids";
in: "Surface Analysis by Auger and X-Ray Photoelectron Spectroscopy", IMPublications, Chichester/UK, 2003, ISBN: 1901019047, S. 235 - 259.

One objective of surface analysis by means of electron spectroscopy is to find, for a given specimen, the number as well as the spatial distribution of a certain chemical species emitting characteristic electrons. This goal must be achieved by quantitative interpretation of the energy and angular distribution of Auger- or photoelectrons (refered to by the catch-all term "signal electrons" in the following) crossing the solid-vacuum interface and eventually reaching the detector. The majority of the signal electrons that reach the detector originate from very shallow depths (of the order of several nanometres) below the surface. This is equivalent to stating that the surface sensitivity of electron spectroscopy techniques is very high. The strong signal electron-solid interaction, that is responsible for the high surface sensitivity, unfortunately also significantly complicates quantitative spectrum analysis: in the course of the transfer of the signal electrons between their point of emission in the solid and escape from the surface, the energy and anagular distribution of signal electrons is significantly modified by scattering processes. Therefore, a model for the signal electron transport is a prerequisite for quantitative interpretation of an experimental spectrum.

In the next section, the elementary processes governing the electron solid interaction will be addressed, and a simple and general model for the effects of electron transport on the spectral shape will be presented in Section 10.3. In this model it will be assumed that the energy, angular and depth distribution of the signal electron sources is known. Ultimately, the aim of such a model is to develop procedures that allow one to gain information on the depth distribution of the sources from experimental spectra. Knowledge about the source energy distribution is also important, not only for fundamental reasons but also for practical work. In Section 10.4, application of the presented model to these problems is discussed.

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