The Kinetic Energy and Angular Distribution of Sputtered Polyatomic Molecules: Outline and Applications

Kinetic energy and angular distribution measurements give information about the emission mechanism of desorbed particles. For a sputtering mechanism, the energy and angular distribution is usually assumed to be of the form: Φ(E,θ)∝ E cosθ/(E+U) 3 . This expression is valid for sputtered atoms and cannot be immediately applied to the sputtering of molecules , where the energy is shared between internal and external degrees of freedom. A model is presented for the kinetic energy and angular distribution of sputtered polyatomic molecules. The formalism is related to an earlier model for sputtered clusters by Konnen, Tip and De Vries [1]. 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. The model shows a continuous transition from a fragmentation dominated behaviour at high kinetic energies to a collision-cascade-like behaviour at low kinetic energies of the sputtered molecules. The model is compared with experimental data on sputtering of Kr 2 , SiCl and SiF.