Parameterization of the mean free path for inelastic scattering of fast electrons

The areas, Iz and It, under the zero-loss peak and under the entire energy-loss spectrum (of a sample of thickness t) are related by the formula:t/ƛ(β) = ln (It/Iz) (1)where ƛ(β) is the inelastic mean free path for all energy losses and for scattering into the collection aperture, of semiangle β. We have used Eq.(l) to experimentally determine ƛ(β) by electron energy-loss spectroscopy of specimens of known composition and thickness. In the case of crystalline samples, the local thickness t was measured by convergent-beam diffraction. In the case of evaporated thin-film specimens, the average thickness was obtained by accurately weighing the substrate before and after deposition. The energy-loss spectroscopy was carried out in CTEM mode with incident energies Eo between 20keV and 120keV, and with collection semiangles in the range 0.2 mrad to 100 mrad.