Elastic Scattering Corrections in AES and XPS. III. Behaviour of Electron Transport Mean Free Path in Solids for Kinetic Energies in the Range 100 eV<E<400 eV

Abstract

Quantitative Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) depend on an accurate knowledge of the correct depth scale of emission of the signal electrons. This depends on both inelastic and elastic scattering processes occurring in the specimen under analysis. A previous paper showed that the depth scale in AES and XPS is significantly influenced by unexpected structure in the transport mean free path for electrons in high-atomic-number elements over the approximate energy range 100–400 eV. This behaviour is implicit in Mott cross-sections, which are known to be reliable and have been used in low-energy electron diffraction (for example) for decades. This paper examines the features of electron–atom elastic scattering over the range of energy and atomic number important in XPS and AES analysis. In particular, the third and fourth partial waves, together with Levinson's theorem are shown to give rise to the structure in the transport mean free path. This is a transport cross-section analogue of the Ramsauer–Townsend effect exhibited at low energies in total elastic scattering cross-sections. © 1997 John Wiley & Sons, Ltd.