On the energy and angular distribution of sputtered polyatomic molecules

Abstract

A model is presented for the kinetic energy and angular distribution of sputtered molecules. After developing the model explicitly for diatomic molecules, a generalization to polyatomic molecules is given. The formalism is related to an earlier model for sputtered clusters by Können, Tip and De Vries, Radiat. Eff. 26 (1975) 23. It is assumed that the individual atoms of a molecule are given an initial momentum according to linear collision cascade properties. If the molecule does not dissociate, it is treated as an entity and carried as such through a planar surface potential barrier. This approach makes the present model more applicable to sputtering of molecules (for which the intramolecular bond energies are generally much larger than the intermolecular energies) than the cluster model of Können, Tip and De Vries. The model shows a continuous transition from a fragmentation dominated behaviour at high kinetic energies to an atomic collision cascade-like behaviour at low kinetic energies of the sputtered molecules. Alternative theoretical approaches are discussed. The model is compared with experimental data. In the appendix a correction to the model of Können, Tip and De Vries is given. © 1987.