Comparisons of calculated and measured effective attenuation lengths for silicon dioxide over a wide electron energy range

We report calculations of effective attenuation lengths (EALs) for Si2p pho toelectrons in silicon dioxide at photoelectron energies between 82 and 138 5 eV. These EALs are compared with measured values reported recently by Shi mada et al. (Surf. Interf. Anal. 29 (2000) 336) at photoelectron emission a ngles of 0 degrees and 55 degrees for photoelectron energies between 140 an d 1000 eV. Close agreement is found between the calculated and measured ene rgy dependencies of the EALs for photoelectron energies between 400 and 100 0 eV. Agreement is also found in the absolute values if the SiO2 film thick nesses in the experiments were increased by 29% or if the inelastic mean fr ee paths used in our calculations were decreased by the same percentage. De viations between measured and calculated EALs for energies between 140 and 400 eV are attributed to the effects of surface-plasmon excitation. Calcula ted EALs for a photoelectron emission angle of 55 degrees were larger than those found for normal photoelectron emission, particularly for low photoel ectron energies, as was found in the Shimada et al. experiments. (C) 2001 E lsevier Science B.V. All rights reserved.