Differential inelastic electron scattering cross sections from experimental reflection electron-energy-loss spectra: Application to background removal in electron spectroscopy.

Abstract

The possibility of extracting absolute inelastic electron scattering cross sections K(T) (differential in energy loss T and path length) for solids from experimental electron spectra is studied. Assuming homogeneous scattering properties for the solid, a formula is found, which allows a direct determination of [\ensuremath{\lambda}L/(\ensuremath{\lambda}+L)]K(T) from a measured reflected electron-energy-loss spectrum (REELS) resulting from a monoenergetic beam of electrons incident on the surface of the solid. Here \ensuremath{\lambda} is the inelastic electron mean free path and L\ensuremath{\simeq}2${\ensuremath{\lambda}}_{1}$ where ${\ensuremath{\lambda}}_{1}$ is the transport mean free path for elastic electron scattering. The formula is applied to experimental REELS spectra of aluminum. The resulting cross sections are discussed in relation to a theoretical calculation based on dielectric-response theory. The determined cross sections are applied to remove the inelastic background signal from Mg--K\ensuremath{\alpha}(h\ensuremath{\nu}\ensuremath{\simeq}1254 eV) and synchrotron-radiation-excited (h\ensuremath{\nu}\ensuremath{\simeq}250 eV) photoelectron spectra of aluminum. The resulting primary excitation spectra are discussed in relation to the results of existing procedures.