Analysis of Reflection Electron Energy Loss Spectra (REELS) for Determination of the Dielectric Function of Solids: Fe, Co, Ni

TL;DR

This paper introduces a straightforward method to extract the dielectric function of solids from REELS spectra by removing multiple scattering effects, enabling accurate optical data retrieval for materials like Fe, Co, and Ni.

Contribution

A novel deconvolution procedure that isolates the dielectric response from REELS spectra without prior surface excitation information.

Findings

The method accurately retrieves dielectric functions for Fe, Co, and Ni.

Results show good agreement with previously reported optical data.

The procedure simplifies analysis of REELS spectra for solid materials.

Abstract

A simple procedure is developed to simultaneously eliminate multiple scattering contributions from two reflection electron energy loss spectra (REELS) measured at different energies or for different experimental geometrical configurations. The procedure provides the differential inverse inelastic mean free path (DIIMFP) and the differential surface excitation probability (DSEP). The only required input parameters are the differential cross section for elastic scattering and a reasonable estimate for the inelastic mean free path (IMFP). No prior information on surface excitations is required for the deconvolution. The retrieved DIIMFP and DSEP can be used to determine the dielectric function of a solid by fitting the DSEP and DIIMFP to theory. Eventually, the optical data can be used to calculate the (differential and total) inelastic mean free path and the surface excitation probability. The procedure is applied to Fe, Co and Ni and the retrieved optical data as well as the inelastic mean free paths and surface excitation parameters derived from it are compared to values reported earlier in the literature. In all cases, reasonable agreement is found between the present data and the earlier results, supporting the validity of the procedure.