Einfluß der Kristallorientierung auf die Plasmonenintensität in Ag und Si

In energy loss measurements of electrons on monocrystals of silver and silicon in transmission the intensity of the volume plasma loss (Ag 3.8 eV, Si 16.6 eV) is found to be dependent on the crystal orientation. By tilting the crystal relatively to the incident beam (in general some degrees) the intensities of the elastic peak (I _el), the volume plasma peak (I _v) and in Ag additionally that of the surface loss (I _s) at 3.1 eV (damped by a carboncoating) show different variations.I _s in Ag andI _v in thick (>150 nm) Si is as expected proportional toI _el, whereasI _v in Ag and thin Si varies much stronger thanI _el, so that the quotientI _v/I_el is not a constant. Presumably an explanation of this phenomenon lies in the dynamic theory of electron diffraction including inelastic processes.