Analysis of angle-resolved electron energy loss in XPS spectra of Ag, Au, Co, Cu, Fe and Si

Angle-resolved XPS measurements on a series of transition metal samples and one Si sample are carried out to investigate the dependence of surface losses on electron exit angle. The inelastic background in the transition metals is analyzed using the universal cross-section λK( T)= BT/( C+ T 2) 2. We find that a consistent primary spectrum F( E) may be obtained for all angles, and for all the metal samples, by adjusting the values of C and B in a well specified way. The variation in C and B models the effect of surface losses on λK( T). The validity of the approach is tested by performing an equivalent analysis of REELS spectra, from which the exact cross-sections can be determined. We find a good agreement between the universal cross-sections and the exact results. For Si the plasmon structure is more narrow and surface effects appear as a separate peak in the loss function. In this case, the procedure described above cannot be applied, and we investigate more qualitatively the magnitude of the surface effects with varying exit angle.