Determination of the Thickness of Nanofilms Using X-Ray Photoelectron Spectroscopy

Resumo

Determination of coating thicknesses whose dimensions lie in the nanometer range is an important analytical application of X-ray photoelectron spectroscopy (XPS). The coating thickness is determined as a result of comparing peak intensities measured using lines corresponding to the coating with those of characteristic substrate lines. It is shown that the error in determining thicknesses using a procedure that completely disregards processes of elastic electron scattering reaches 50%. At present, the influence of elastic scattering processes is taken into account by replacing the inelastic mean free path with the fitting parameter called the effective attenuation length. Physical phenomena occurring in the case of the inclusion of an elastic photoelectron scattering channel are analyzed in this paper. Two approaches to the description of XPS spectra are considered: the first one is implemented using invariant embedding methods, and the second one used the method of discrete ordinates with the matrix exponent. On the basis of the first method, the influence of multiple elastic-scattering events on the XPS energy spectra is studied. The second one shows a high effectiveness when calculating no loss peaks of photoelectrons emitted by multilayer samples.