Quantitative analysis in X-ray photoelectron spectroscopy: Influence of surface excitations

A take-off-angle-dependent convolution formula has been derived to obtain angle-resolved XPS spectra by including the effect of surface excitations into the Landau formula. An extended Drude dielectric function is employed to estimate the electron differential inverse mean free paths for bulk excitations. The same dielectric function is applied to evaluate the probability of surface excitations for emitted electrons by including the recoil effect and without the small-scattering-angle approximation. Through numerical calculations for Au 4f XPS spectra the effects of surface excitations have been shown to be significant in XPS spectra. Moreover, the influence of surface excitations on the energy-loss structure within 30 eV is enhanced for large take-off angles. Calculated spectra that include the surface excitations are in better agreement with experimental data.