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-ɛ(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 Fe28Ni72 are similar to those of Fe51Ni49, even though there is a small peak shift from 18.5 eV for Fe51Ni49 to 18.7 eV for Fe28Ni72. A plot of n, k, ɛ1, and ɛ2 shows that the QUEELS-ɛ(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 (Fe28Ni72), ɛ1, and ɛ2 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.