Influence of surface excitations on electrons elastically backscattered from copper and silver surfaces

Abstract

The influence of surface excitations on electrons elastically backscattered from solid surfaces is investigated. Elastic-scattering differential cross sections are calculated using the partial-wave expansion method and the finite difference techique for solid atoms with the Hartree-Pock-Wigner-Seitz potential. An extended Drude dielectric function which allows the characteristic oscillator strength, damping constant, and critical-point energy for each subband of valence electrons is employed to estimate electron inelastic mean free paths for volume excitations. The same dielectric function is applied to evaluate the probability of surface excitations for incident and escape electrons by including the recoil effect without the small-angle approximation. Results of Monte Carlo simulations on the elastic reflection coefficient and the angular distribution of electrons elastically backscattered from Cu and Ag surfaces are presented. It is revealed that surface excitations significantly reduce the elastic reflection coefficient for lowenergy electrons, but less significantly influence the angular distribution for large escape angles. Our results agree very well with experimental data.

Angular and energy dependences of the surface excitation parameter for electrons crossing a solid surface

“…Previous studies showed that surface excitations contributed significantly to the spectra of electrons backscattered from solid surfaces [1][2][3]. Therefore, an account of surface excitations in the analyses of electron spectroscopies should be established theoretically.…”

Angular and energy dependences of the surface excitation parameter for semiconducting III–V compounds

“…Recent studies on the energy-loss spectra [1][2][3] of electrons reflected from solid surfaces have demonstrated that the contribution from surface excitations was important for electron energies from a few hundred eV to several keV, especially with obliquely incident or escaping electrons. Therefore, surface excitations should be included in the analyses of electron spectroscopies.…”

Experimental estimation of surface excitation parameter for surface analysis

“…In latter years some fundamental papers contain comprehensive reviews of the literature. 1 -5 Much less has been published on experiments 6 -13 using EPES 7,8 , REELS 6,9,10,12,13 and angular REELS. 11 Very few P se experimental data have been published.…”