Energy shift and broadening of the spectra of electrons backscattered elastically from solid surfaces

In the present work our experimental results on the energy shifts and energy widths (full width of half-maximum) of the quasi-elastic peaks (1-5 keV) obtained using a high-energy-resolution electron spectrometer and different (C, Si, Ni and Au) surfaces are compared with those calculated by assuming single elastic scattering on free atoms having a Maxwell-Boltzmann thermal velocity distribution. There is a good agreement in the case of the energy shifts as well as for the energy broadenings obtained using higher atomic number polycrystalline samples (Ni, Au). In the case of Si, however, the measured energy broadening is systematically larger by 15-20% than the calculated broadening for the whole primary beam energy range. Compared with the calculated values, considerably larger broadenings (by 30-60%, depending on the primary beam energy) were observed for carbonic samples. The contribution of the multiple elastic scattering to the yield of the electrons backscattered elastically, and the effect of the multiple scattering on the energy shifts and Doppler broadenings, have been determined using Monte Carlo simulations. Our results show that multiple scattering causes only small changes in energy shifts and energy broadenings of elastic peaks in the case of the samples and primary electron energy region studied. Copyright (C) 2001 John Wiley & Sons, Ltd.