LabAdviser/314/Microscopy 314-307/Technique/EELS: Difference between revisions

The fast electron beam can lose energy by exciting electrons in the outer or inner atomic shells of atoms to higher unoccupied energy states. Outer-shell single electron excitations can be seen as peaks at energies up to ~ 50 eV in the energy-loss spectrum. At higher energies the scattering intensity decreases according to a high power of the energy-loss and inner-shell electron excitations are seen as edges superimposed on this smoothly decreasing background (marked as ionisation edge in Fig. 1). In addition, the energy-loss spectrum can contain peaks corresponding to plasmon excitations. Plasmons can be excited within the specimen, i.e. a bulk plasmon, or at an interface, i.e. an interface plasmon. Plasmons generally occur in the range 5 – 30 eV, at energies higher than the band gap of the material. The first 50 eV of an energy-loss spectrum is usually referred to as the low-loss region. Higher energy-loss regions containing inner-shell ionisation edges are usually referred to as the core-loss region.