Experimental determination of electron effective attenuation lengths in silicon dioxide thin films using synchrotron radiation II. Effects of elastic scattering

Abstract

The effective attenuation lengths (EALs) of photoelectrons in thin silicon dioxide films on an Si(100) substrate were measured as a function of electron energy using synchrotron radiation as an energy-tunable excitation source. The ratios of EALs to inelastic mean free paths (IMFPs) calculated from optical data were independent of electron energy from 140 to 1000 eV when the analyzer axis was normal to the sample surface and the angle between the incident x-rays and the surface normal was 55°. This result indicates that the effects of elastic electron scattering (in causing the EAL to be less than the corresponding IMFP) were independent of electron energy for this configuration. The EALs measured with normally incident x-rays and electron emission at 55° with respect to the surface normal were larger than EALs for the other configuration. In particular, the difference for the EALs at the two configurations was ∼25% for electron energies below 200 eV. The angular range suitable for satisfactory angle-resolved analyses with x-ray photoelectron spectroscopy should therefore be limited to < 55° when the electron energies are less than ∼500 eV. Copyright © 2000 John Wiley & Sons, Ltd.