Untersuchungen zur normalen und anomalen Absorption von Elektronen in Silizium- und Germanium-Einkristallen bei verschiedenen Temperaturen

Abstract

Absolute filtered intensities of the electrons scattered elastically in thin platelike Si and Ge crystals have been measured. From the intensities of the primary and the Bragg reflected beams measured as a function of incident direction the coefficients for normal and anomalous absorption can be obtained with good accuracy, using the two beam approximation of the dynamical theory. Moreover, for Si the foil thickness and structure potentials can be deduced which are in agreement with the thickness determined optically and with calculated structure potentials resp. The results partly are influenced by multiple beam effects, which, however, are shown to be describable by Bethe's second approximation.

All absorption coefficients, measured for different reflections and different crystal temperatures, show an increase with temperature, which is rather weak for Si and stronger for Ge. This shows that there is an influence of temperature diffuse scattering on normal and especially on anomalous absorption, which increases with atomic number. The results can be interpreted quantitatively, using simple models for the various contributions to the absorption coefficients (excitation of single electrons, plasmons and phonons).