Quantitative analysis of reflection electron energy loss spectra to determine electronic and optical properties of Fe–Ni alloy thin films

Electronic and optical properties of Fe-Ni alloy thin films grown on Si (1 0 0) by ion beam sputter deposition were studied via quantitative analyses of reflection electron energy loss spectra (REELS). The analysis was carried out by using the QUASES-XS-REELS and QUEELS-ε(k,ω)-REELS softwares to determine the energy loss function (ELF) and the dielectric functions and optical properties by analyzing the experimental spectra. For Ni, the ELF shows peaks around 3.6, 7.5, 11.7, 20.5, 27.5, 67 and 78 eV. The peak positions of the ELF for Fe ₂₈Ni ₇₂ are similar to those of Fe ₅₁Ni ₄₉, even though there is a small peak shift from 18.5 eV for Fe ₅₁Ni ₄₉ to 18.7 eV for Fe ₂₈Ni ₇₂. A plot of n, k, ε ₁, and ε ₂ shows that the QUEELS-ε(k,ω)-REELS software for analysis of REELS spectra is useful for the study of optical properties of transition metal alloys. For Fe-Ni alloy with high Ni concentration (Fe ₂₈Ni ₇₂), ε ₁, and ε ₂ have strong similarities with those of Fe. This indicates that the presence of Fe in the Fe-Ni alloy thin films has a strong effect.