LEED OBSERVATIONS OF (11) BEAM FROM (100) SURFACES OF SOME NACL-TYPE CRYSTALS

Low energy electron diffraction patterns from the (100) surfaces of crystals of RbBr, KCl, NaF, KBr, NaCl, LiF and MgO have been observed as a function of electron energies between 30 eV and 1000 eV. It was found that (11) reflections occur at low voltages, even in cases of crystals in which the atomic scattering amplitudes are such that (11) reflections should be too weak to be observed. The (11) reflections were found to become very weak above 59 eV for RbBr, 100 eV for KC1 and 195 eV for NaF. Published work on NaCl suggests that the (11) spot persists to above 260 eV. It is shown that kinematical scattering theory is most suitable when the ratio of cation to anion diameters is near to unity, because then the transparency will be the greatest. © 1968.