Inelastic Electron Scattering and Spectroscopy
Chapter 4 presented elastic scattering of electrons, and Chap. 5 presents inelastic scattering. The different physical mechanisms important for electron energy loss spectrometry (EELS) are described—interband transitions, plasmons, and core excitations. Near-edge structure and extended fine structure are useful methods for studying the chemical composition and local structure of materials, and these are developed with examples. The operation of an EELS spectrometer and the intensities of measured spectra are explained. Energy-filtered imaging is described. EELS core spectra originate from primary ionizations of atoms, and the subsequent x-ray emissions are the basis for energy dispersive x-ray spectrometry (EDXS). It is fortunate that the EDS method gives good sensitivity for elements over much of the periodic table—the probabilities for ionization and for x-ray emission have strong, but compensating, chemical trends. The EDS method is a workhorse tool for fine-scale chemical analysis of materials. Some practical issues are described, with discussions of spatial resolution, accuracy and sensitivity of EDS methods.