Inelastic mean free path measurements of electrons near nickel surfaces

The inelastic mean free path of electrons near solid surfaces is a key parameter in quantitative analyses by commonly used surface-sensitive methods. There are experimental and theoretical methods to determine reliable inelastic mean free path values. The elastic peak electron spectroscopy method allows the determination of the inelastic mean free path values in agreement with the ASTM definition. This method is based on a theoretical relationship between elastic backscattering probability and the inelastic mean free path. In the present contribution, we study statistical and systematic uncertainties of the measured backscattered intensities from Ni foils prepared by rolling and cutting of the bulk material and of annealing. Depending on the sample preparation, the measured intensities vary by a factor of 2 for 200 eV electron energy, whereas at >1000 eV the deviations are much smaller. This behaviour, explained by the different surface morphology and different grain sizes, has an important impact on measured inelastic mean free path values. Investigation of Ni foils is of a great interest due to frequent use of this metal as a standard material in the elastic peak electron spectroscopy method.