Energy dependent studies of anisotropic atomic sputtering of Ni(111)

The anisotropic ejection of atoms sputtered from a Ni(111) surface by Ar⁺ ions of 1.1 keV was investigated by angle- and energy-resolved secondary neutral mass spectrometry (SNMS). The angular distribution of sputtered atoms exhibits three different peaks which correspond to a preferred emission along the close packed [111]-, [110]- and [100]-directions of the crystal, respectively. The intensity as well as the location of the "spots" are shown to depend strongly on the ejection energy E of the sputtered atoms. Also, the energy distributions measured in and outside of the spot directions are found to differ significantly. The results are reproduced at least qualitatively by a molecular dynamics simulation using a many-body embedded atom interaction potential.