Surface Analysis II. Electron Spectroscopy Methods

Electron spectroscopy probes the electronic structure of the surface through analysis of the energy spectra of the secondary electrons emitted from the sample. The secondary electrons are created generally by bombarding the surface with electrons or photons (other particles are also used (for example, ions or atoms), but seldom). The typical energies of secondary electrons analyzed in surface electron spectroscopy belong to the range 5–2000 eV. The surface sensitivity of electron spectroscopy stems from the fact that electrons with energies in that range are strongly scattered in solids. Figure 5.1 shows a plot of experimental values of the electron inelastic mean free path versus the electron kinetic energy. Though the data are energy and material dependent the magnitude of the inelastic mean free path in the whole energy range is of the order of several dozens of A and in the favorable energy interval (~20–200 eV) is less than 10 A.