Determination of effective electron inelastic mean free paths in SiO 2 and Si 3N 4 using a Si reference

Elastic peak electron spectroscopy (EPES) provides inelastic mean free path (IMFP) values in the near-surface region. Such values, which will be called effective IMFPs, might be different from these derived from bulk parameters. In this work we derive effective IMFP values from EPES measurements in the range of 300-2000 eV for SiO ₂ and Si ₃N ₄ using a Si reference. Corrections for surface excitation are applied. Our effective IMFP values agree well with those calculated from optical data in the case of SiO ₂; that is, the ion sputtering does not alter the SiO ₂ surface significantly. On the other hand, systematic deviations between our data and those provided by a predictive formula were found in the case of sputtered Si ₃N ₄. These differences are attributed to alteration in the surface layer caused by sputtering.