title: Low-energy electron reflectivity from graphene: first-principles computations and approximate models.
abstract: A computational method is developed whereby the reflectivity of low-energy electrons from a surface can be obtained from a first-principles solution of the electronic structure of the system. The method is applied to multilayer graphene. Two bands of reflectivity minima are found, one at 0-8 eV and the other at 14-22 eV above the vacuum level. For a free-standing slab with n layers of graphene, each band contains n-1 zeroes in the reflectivity. Two additional image-potential type states form at the ends of the graphene slab, with energies just below the vacuum level, hence producing a total of 2n states. A tight-binding model is developed, with basis functions localized in the spaces between the graphene planes (and at the ends of the slab). The spectrum of states produced by the tight-binding model is found to be in good agreement with the zeros of reflectivity (i.e. transmission resonances) of the first-principles results.
authors.affiliation: Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA. feenstra@cmu.edu
authors.forename: R M
authors.initials: RM
authors.lastname: Feenstra
authors.forename: M
authors.initials: M
authors.lastname: Widom
keywords: Electron reflectivity; Graphene; Low-energy electron microscopy; Surface