Interband transitions in ZnO observed in low energy electron spectroscopy
Using a high resolution two-axis-spectrometer energy loss spectra of electrons specularly reflected from (1¯100) ZnO-surfaces have been investigated. The electron impact energy was varied between 25 and 60 eV. The spectra show a strong dependence on the orientation of thec-axis with respect to the plane of incidence. The dependence of the loss intensities on the angle of incidence and the shape of the spectra can be qualitatively described by the “Dielectric Theory”.Contrary to optical reflection measurements the excitation of excitons could not be observed in agreement with the existence of a surface barrier for excitons.