Energy-filtered HREM images of valence-loss electrons

A theory is proposed to include the effects of valence excitations in electron image simulations for high-resolution electron microscopy (HREM) based on the single inelastic scattering model.Under the small thickness approximation, this general theory reduces to the simplified theory of perfectly delocalized inelastic scattering model, in which the image can be considered to be an incoherent sum of those incident electrons of different energies weighted by the intensity distribution in the electron energy-loss spectrum from the area where the pattern was taken.The main effect of valence-loss is to introduce a focus shift due to chromatic aberration, resulting in contrast variation (or reversal) of the image.The generalization of this theory for simulations of interface images with considering surface and interface plasmon excitations is given.Calculations for GaAs surface profile images are demonstrated to show the effect of inelastic localization.