A bond breaking model for secondary ion emission

In this paper we propose a bond breaking model for secondary ion emission during ion beam sputtering from partially ionic compounds such as oxides. The electronic interaction is assumed to be local and the charge transfer happens at the crossing of the neutral potential curve with the ionic potential curve, as the chemical bond between the sputtered atom and its neighbors is broken. The model uses the Landau-Zener curve crossing theory and correctly predicts the relation between the ionization probability P+ and the ionization potential, and the dependence of P+ on the emission energy and the isotopic mass. A comparison is made with the electron tunneling model which succesfully describes the secondary ion emission from metals. The common physical basis of these two models is discussed. © 1986 Elsevier Science Publishers B. V. (North-Holland Physics Publishing Division).