Plasmon peak inhomogeneous broadening in reflection electron energy loss spectroscopy from carbon materials

In addition to the damping effect on plasmon peak broadening in reflection electron energy loss spectroscopy (REELS), the effect of inhomogeneous broadening is considered. The analysis of experimental data from highly oriented pyrolytic graphite (HOPG) shows that the contribution of inhomogeneous broadening is of the same order as the contribution associated with damping. In other words, the width of plasmon peaks cannot be ascribed only to damping, which is just one among several other contributions in this respect. At variance with other broadening contributions, however, damping is responsible not only for the width of plasmon peaks but also for their energy. For this reason, by showing that accounting for inhomogeneous broadening leads to decrease of the damping parameter,we also show that the plasmon peak-shift associated with damping is less than one could expect otherwise.