Assessment of the extent of atomic mixing from sputtering experiments

Ion-bombardment-induced atomic mixing effects are investigated, taking into account the depth dependence of the quantities of relevance. It is shown that in the dilute limit the fluence dependence of tracer (overlayer) atom removal is characterized by an exponential tail. The slope σi of this tail is determined by the differential escape rate of the dopant atoms, as well as the shape of the ’’mixing profile.’’ The extent of mixing (and selective sputtering) in a given system can be characterized by the ratio Ym/σi, where Ym is the matrix sputtering yield. Intermixing of Au with Si is found to be much stronger than expected on the basis of mere collisional relocation of atoms. Some comments are made concerning the use of Rutherford backscattering spectrometry and Auger electron spectroscopy for the determination of escape rates and selective sputtering effects.