Scanning Electron Microscopy


We present a review of the Auger emission induced from light elements (Mg, Al, Si) bombarded by ions of intermediate energy (1 keV - 200 keV). The different physical phenomena at the origin of Auger emissions are outlined, in particular the mechanism of molecular excitation responsible for the production of inner-shell vacancies in collisions between two complex particles and the processes of Auger decay and electron transport in the solid. Auger spectra partially consist of L23VV electrons corresponding to decays in the bulk; this part is similar to that observed from electron-induced Auger spectra. Superimposed on this broad structure appear different narrow lines due to de-excitations from excited sputtered atoms. These atomic-like lines are assigned to different L23MM or [(L23)2MM] Auger transitions. The dependence of the width and shift of these lines on different parameters (e.g., ionic energy, emission polar angle) is interpreted by Doppler effect. On the other hand, the experimentally determined L23VV and L23MM Auger yields are compared to values calculated by computer simulations of collision cascades (from EVOLVE and MARLOWE codes). Lastly the azimuthal and polar angular distributions of both L23VV and L23MM Auger electrons are analysed by taking into account the important role of ion-induced surface topography.

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