ENERGY-DEPENDENCE OF THE DIFFERENT ELECTRON EMISSIONS BACKSCATTERED FROM POLYCRYSTALLINE MOLYBDENUM

The energy dependence of the emission yield of electrons backscattered from a clean polycrystalline molybdenum sample has been studied using a dispersive hemispherical analyser (incidence angle beta = 70-degrees; collection angle theta = 0-degrees). True secondaries, Auger electrons, elastic peak and background detected in the N(E) mode were investigated. Experimental results related to the elastic scattering of primary electrons are in good agreement with theoretical treatments (simple diffusion model and Monte Carlo simulation of multiple scattering). It is found that elastically reflected electrons mainly arise from single collision processes with a maximum of the emission yield at a primary energy E(p) congruent-to 300 eV. The behaviour of the Mo-MNN Auger signal normalized by the primary current is compared to the energy dependence of the Auger peak/background ratio. These two normalization procedures lead to some differences mainly due to the transfer of the inelastic contribution of the background toward higher kinetic energies when E(p) is increased. The dependence on the primary energy of the true secondary emission is closely related to the one recorded for the total backscattered coefficient deduced from the measurements of primary and sample currents. Threshold effects at an energy corresponding to the Mo-3d inner level are hardly detected. Furthermore, a rough estimation of the relative contributions of the different electrons involved in the N(E) backscattered spectra is proposed.