Effective attenuation lengths of low energy electrons in MgO thin films

The effective attenuation length (EAL) of electrons in MgO films has been measured in the (5.5-28) eV energy range by the over-layer method and correlated with the band structure of the material. As expected, the EAL is found to increase when the electron energy is decreased, but the obtained values are smaller than those predicted by the universal curve. The comparison of the experimental results with calculated optical properties available in the literature suggests that, for energies lower than 20 eV, the relevant scattering mechanisms are described by the imaginary part of the dielectric function, accounting in particular for the steep increase of the EAL for energies smaller than the insulator band gap.