Abstract
A simple method is proposed for inclusion of inelastic effects (electron absorption) in computations of low-energy electron reflectivity (LEER) spectra. The theoretical spectra are formulated by matching of electron wavefunctions obtained from first-principles computations in a repeated vacuum–slab–vacuum geometry. Inelastic effects are included by allowing these states to decay in time in accordance with an imaginary term in the potential of the slab, and by mixing of the slab states in accordance with the same type of distribution as occurs in a free-electron model. LEER spectra are computed for various two-dimensional materials, including free-standing multilayer graphene, graphene on copper substrates, and hexagonal boron nitride on cobalt substrates.
Highlights
Low-energy electrons (0–300 eV) have been employed as a probe of the geometric and electronic structure of surfaces
A simple method is proposed for inclusion of inelastic effects in computations of low-energy electron reflectivity (LEER) spectra
LEER spectra are computed for various two-dimensional materials, including free-standing multilayer graphene, graphene on copper substrates, and hexagonal boron nitride on cobalt substrates
Summary
Low-energy electrons (0–300 eV) have been employed as a probe of the geometric and electronic structure of surfaces. Since these electrons interact very strongly with atoms, any electrons that are elastically scattered from the surface necessarily originate from only the top few surface layers, providing a sensitive probe of the nearsurface region. The technique of low-energy electron diffraction (LEED) has been developed by many workers, both experimentally and theoretically.. The intensity of the diffracted beams as a function of incident energy, IgðEÞ, can be measured. Such IgðEÞ curves contain valuable information on the geometric structure of the surface, in particular, for cases when the surface is reconstructed giving rise to fractional p and q values. In most cases, the actual atomic positions are very difficult to directly deduce from simple inspection of the IgðEÞ curves, so that it is necessary to perform a detailed comparison between experimentally measured and theoretically predicted curves in order to determine the structure.
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