XPS is currently used to determine the atomic composition of material surfaces, and the nature of the atom bounds. But XPS also reveals an important signal corresponding to photoelectrons which interacted with the material, basically through plasmon excitations. These plasmon are due to the collective behavior of the valence or conduction electrons in the material, and the cross-section of this interaction is basically proportional to the imaginary part of the inverse of the dielectric function of the material. Thus, the analysis of the photoelectron-energy loss spectra (PEELS) leads to the determination of the dielectric function of the material. We developed a numerical method based on the use of the Fourier transform to determine this dielectric function and we successfully applied it to several materials, such as Aluminum and black Phosphorus. We shall explain the method, focusing on the solving of critical difficulties, discuss some of our results and present some perspectives.
Universidade Federal da Bahia (UFBA)
Campus Universitário de Ondina, Salvador-BA
Brasil CEP: 40210-340.