Electron Inelastic Scattering in Surface Analysis

This paper discusses the recent progress in electron inelastic mean free paths (IMFPs) calculations with the dielectric response function and optical energy loss function (ELF) as key parameters. For most materials, the IMFP values calculated using various algorithms show good agreements with each other in the energy region above 300 eV; however, a large difference exists in the energy region under 200 eV. The energy dependencies of IMFPs calculated from optical ELFs can be expressed using the modified Bethe equation for energy regions between 50 eV and 200 keV; the material dependence of IMFPs can be expressed by the TPP-2M equation. For IMFP calculations, the treatments and evaluations of the electron exchange effect, the effect of energy gap in the energy loss function, and the associated integral region remain important issues that will need to be addressed in the future.