Extracting detailed information from reflection electron energy loss spectra

We use REELS (reflection electron energy loss spectroscopy) measurements at relatively large energies (up to 40 keV) and good energy resolution (0.3 eV) to extract the bulk and surface loss function for Au, Mo and Ta. For these cases there are small, but significant deviations between the electron-based estimates of the dielectric function as published by Werner et al. (J. Phys. Chem. Ref. Data 38 (2009) 1013), and the corresponding photon absorption/reflection based estimates. The present, higher-resolution electron-based measurements reveal more of the fine structure in the differential inverse inelastic mean free path (DIIMFP) and the differential surface excitation probability (DSEP). The same fine-structure is visible in the photon-derived estimates of the bulk and surface loss function, quantities closely related to the DIIMFP and DSEP. Thus we demonstrate that it is indeed possible to derive these fine details of the surface and bulk loss function with REELS, underlining its potential for extracting information on the dielectric function of materials.