Messung der Elektronenbeugungsintensitäten polykristalliner Aluminiumschichten bei tiefer Temperatur und Vergleich mit der dynamischen Theorie

By means of a retarding field apparatus the electron diffraction intensities of a polycrystalline Aluminium-foil have been measured for different electron energies between 17 and 50 kev. The specimen was kept at 154 °K and the thickness of the crystallites was about 280 Å. It has been shown that the high index reflections behave kinematically, while the first order reflections e.g. (111), (200)] are much influenced by dynamical extinction effects which can be explained very well by the dynamical two beam approximation. Also the intensities of the higher orders e.g. (222), (400)] of the strong reflections show marked deviations from the kinematical values. This intensity deficit can be interpreted by multiple scattering processes due to systematic interactions. The experimental results are compared with the second Bethe approximation (introduction of dynamic potentials) as well as with the second Born approximation where double scattering processes within the crystal are taken into account.