MECHANISTIC STUDY OF ATOMIC DESORPTION RESULTING FROM THE KEV-ION BOMBARDMENT OF FCC(001) SINGLE-CRYSTAL METALS

Energy-resolved angular distributions of Ni and Rh atoms desorbed by k eV Ar+ ion bombardment have been measured using multiphoton resonance ionization detection. The experimental spectra were simulated using mo lecular-dynamics calculations which are based on the molecular-dynamic s/Monte Carlo corrected effective-medium interaction potential. Import ant collision events were identified using a recently developed graphi cal utility which allows easy visualization of atomic motions subseque nt to bombardment. Three major microscopic ejection mechanisms were de termined, each of which is categorized into three additional interacti ons. The features which make up the polar angle spectra are assigned t o one of these mechanisms. We find that the majority of particles ejec t due to a collision with an atom from one layer below (Delta(1) mecha nism). A mechanism involving a collision due to an atom from the same layer, however, is responsible for a shift in peak position with energ y. This investigation strongly reinforces the view that the inherent r egistry of the atoms in the crystal lattice is the crucial factor in d etermining the dominant microscopic sequences of events which lead to ejection as well as the macroscopically observable quantities.