Effects of Interaction Potential on Elastic-Electron-Scattering Parameters in Surface-Sensitive Electron Spectroscopies
Aleksander Jablonski, Cedric J. Powell
The interaction potential for elastic scattering of electrons by atoms influences the magnitudes of calculated elastic-scattering cross sections. We have investigated the influence of two choices of interaction potential, the Thomas-Fermi-Dirac (TFD) potential and the Dirac-Hartree-Fock-Slater (DHFS) potential, on the differential elastic-scattering cross sections and the total elastic-scattering cross sections for the elastic scattering of 1000 eV electrons by six representative elements (Be, C, Al, Cu, Ag, and Au). The differential cross sections for the two potentials varied by up to a factor of three for scattering angles less than 30 , while total cross sections varied between 15% and 61%. In contrast, transport cross sections (which emphasize large-angle scattering events) calculated from the two potentials differed by between 1% and 8.5% for the six elements. We compared results of Monte Carlo calculations by elastic-backscattering probabilities of normally incident 1000 eV electrons on Be, C, Al, Cu, and Au with the two potentials, and found percentage differences in these probabilities varying between 1.2 and 9.4% for emission angles of 45 10 . Monte Carlo calculations were also made of signal intensities in X-ray photoelectron spectroscopy (XPS), emission depth distribution functions (EDDFs) in XPS, and mean escape depths (MEDs) in XPS for selected photoelectron lines from Be, C, Al, Cu, Ag, and Au using the TFD and DHFS potentials and a common XPS configuration. The percentage deviations in the results for the two potentials did not exceed 2% for the signal intensities, were generally less than 10% for the emission depth distribution functions, and less than 2.5% for the mean escape depths. The lack of sensitivity of the Monte Carlo results to interaction potential is due to the fact that small-angle elastic-scattering events are not significant in the transport of signal electrons in XPS and Auger electron spectroscopy (AES). We point out that XPS signal intensities and EDDFs and MEDs for both XPS and AES can be calculated from a solution of the Boltzmann equation within the transport approximation. This approach is useful for the correction of elastic-scattering effects in quantitative AES and XPS because the only parameter used to describe elastic-scattering effects is the transport cross section (which is relatively insensitive to the choice of interaction potential).
aluminum, Auger electron spectroscopy, carbon, computer simulations, copper, elastic, electron-solid interactions, Gold, Monte Carlo simulations
and Powell, C.
Effects of Interaction Potential on Elastic-Electron-Scattering Parameters in Surface-Sensitive Electron Spectroscopies, Surface Science
(Accessed December 8, 2023)