TOWARDS A UNIVERSAL CURVE FOR ELECTRON ATTENUATION - ELASTIC-SCATTERING DATA FOR 45 ELEMENTS

The attenuation parameter (AP), which quantitatively describes the influence of elastic electron scattering on the electron spectroscopies, has been calculated for 45 elements (Be, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Ba, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Pb) and for energies of 250, 500, 1000 and 1500 eV. The calculations were performed with a Monte Carlo algorithm in which elastic scattering is modelled by use of the partial wave expansion method. The results show a linear relationship between the AP and the inelastic mean free path (IMFP), and a linear least-squares fit of the data provides a simple formula to calculate the AP for a given material and energy. The depth distribution function (DDF), which in the most general sense describes the attenuation properties of signal electrons, can be calculated analytically using this AP. The possibility of using the calculated AP values in combination with this DDF to extract IMFP data from an overlayer experiment has also been explored. Evidence is found, and discussed, that the presented algorithm can be used to convert IMFPs to attenuation lengths (AL).