Comparison of Energy-Loss Functions from Reflection Electron Energy-Loss Spectroscopy Spectra with Surface and Bulk Energy-Loss Functions: in Case of Cu

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Effective energy-loss functions (EELFs) are derived from experimental reflected electron energy-loss spectroscopy (REELS) spectra measured at different primary energies for copper using an extended Landau approach. The peak profiles of EELFs are between those of the surface and bulk energy-loss functions. Fine structures overlapping on an elastic peak and corresponding to interband transitions are obtained. It is found that the plasmon peak at 7–9 eV shifts to a higher energy with an increase in primary energy; this is because peak consists of the surface and bulk plasmon excitations at ${\sim}7$ eV and ${\sim}8.3$ eV, which overlap each other to be observed as a single peak. The double peak structure at 15–30 eV results from the synergistic action of collective oscillations including the participation of $d$-band electrons and high-energy band–band transitions. The excitation and ionization of $3p$ inner-shell electrons form two other humps at ${\sim}57$ eV and ${\sim}77$ eV. A Monte Carlo simulation using EELFs has been applied to reproduce the experimental REELSs with considerable success.
2004-10-15