Precision Determination of Surface Plasmon Dispersion on Al(111) Films via Inelastic Low-Energy Electron Diffraction

Abstract

A high-precision method of analyzing inelastic low-energy diffraction (ILEED) intensities is proposed for the determination of the surface plasmon dispersion relation from measured intensities. It is a refinement of a previously used procedure based on the two-step model of ILEED. The method is applied to analyze seven independent sets of ILEED intensities associated with electrons scattered in the specular beam from Al(111). All seven analyses are consistent with the surface-plasmon dispersion ħωs(p‖)=10.5+2p‖ and damping Γs(p‖)=1.85+3p‖. Energies are measured in eV and momenta in Å−1. If consistency with all seven data sets is required, all parameters in both the dispersion and damping are determined uniquely to an accuracy of 3% in the constant term and 50% in the term linear in p‖. No term quadratic in p‖ is required in either the dispersion or the damping.