Determination of effective electron inelastic mean free paths in SiO2 and Si3N4 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 SiO2 and Si3N4 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 SiO2; that is, the ion sputtering does not alter the SiO2 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 Si3N4. These differences are attributed to alteration in the surface layer caused by sputtering.