Auger electron yields induced by channeled ions at grazing incidence

The spectroscopy of Auger electrons induced by channeled ions is discussed by experiments and computer simulations as regards its applicability in surface structure studies. A Ni(110) surface bombarded with 150 keV protons under axial surface channeling and planar channeling conditions is used as an example. It is shown that axial surface channeling provides an excellent surface sensitivity for the application to surface structure analysis and location of adsorbed atoms, whereas planar channeling due to larger grazing angles of incidence to the surface does not. The influence of the impact parameter dependence of the ionization probability on the channeling dips is investigated by means of two different Auger lines: nickel M₂₃VV and L₃VV. The results yield a criterium for the selection of the most suitable Auger transition for the application of this technique. The influence of the mean free path of the induced Auger electrons is examined and the effect of thermal vibrations and surface steps is discussed.