Energieverlustmessungen an III–V-Verbindungen

Energy loss measurements with 55 keV electrons were made on the III–V compounds GaP, GaAs, GaSb, InAs and InSb. Retardation effects become important, because for these substances the condition for Cerenkov radiation is fulfilled. These produce an additional peak in the energy loss spectrum; its angular distribution and its dependance on the foil thickness were measured. The experimental results are in good agreement with the energy loss probability calculated by Kröger taking into account the retardation. Retardation- and surface effects vanish for scattering anglesθ≧0.6; 0.6 mrad. Then it is possible to determine the energy loss function Im(1/?). By means of the KramersKronig analysis the optical constants? ₁ and? ₂ were computed. The values are in agreement with data obtained from optical measurements.