Ion-matter interactions by MD simulations making use of reactive force fields

Abstract

In the field of SIMS, ion-matter interactions have been largely investigated by numerical simulations like TRIM (or other programs using the binary-collision approximation) or molecular dynamics (MD) simulations. For MD simulations related to inorganic samples, mostly classical force fields assuming stable bonding structure have been used. In materials science, level-three force fields capable of simulating the breaking and formation of chemical bonds have recently been conceived. One such force field has been developed by Kieffer et al. 1–4 This potential includes directional covalent bonds, Coulomb and dipolar interaction terms, dispersion terms, etc. Important features of this force field for simulating systems that undergo significant structural reorganization are: (i) the ability to account for the redistribution of electron density upon ionization, formation, or breaking of bonds, through a charge transfer term; and (ii) the fact that the angular constraints dynamically adjust when a change in the coordination number of an atom occurs. In this work, we will present preliminary results of this potential, parameterized for silicon, for the simulation of atomic trajectories in samples subject to ion bombardment. Compared to normal force fields, ion-matter interactions as well as the sputtering of matter are expected to be described more accurately, especially when using reactive primary ions (oxygen or cesium) at low-impact energies. Copyright © 2010 John Wiley & Sons, Ltd.