A comparison of molecular dynamic simulations and experimental observations: the sputtering of gold {1 0 0} by 20 keV argon C.M. McQuaw * , E.J. Smiley, B.J. Garrison, N. Winograd Department of Chemistry, The Pennsylvania State University, 184 Materials Research Institute Building, University Park, PA 16802, USA Available online 24 May 2004 Abstract In order to further illuminate the sputtering process, the bombardment of Au {1 0 0} by 20 keV Ar is investigated using molecular dynamics (MD) simulations. The MD results are compared to experimental observations discussed by M.W. Thompson in his recent review of the atomic collision cascade process [Vacuum 66 (2) (2002) 99]. In his review, Thompson explains characteristics of experimental time-of-flight (ToF) and polar distributions using ejection mechanisms. Using mechanisms deduced from the MD results the ToF distributions are divided at 70 ms with atoms sputtered by direct recoil at shorter ToF and atoms sputtered by focused collision sequences at longer ToF. Surface lens assisted focusing arises from impacts along crystal symmetry lines (slice impact points) and results in a peak at surface normal in the polar distribution. These conclusions help to clarify the experimental observations made by Thompson and contribute to the overall description of sputtering. # 2004 Elsevier B.V. All rights reserved. Keywords: Molecular dynamics; Time-of-flight; Ejection mechanism; Sputtering 1. Introduction A fundamental understanding of the events that lead to sputtering is valuable in explaining experimental results. Presented here is an investigation into the mechanisms involved in the sputtering of Au {1 0 0} by 20 keV Ar using molecular dynamics simulations. The recent article by Thompson that discusses collision cascades [1] inspired this work. The results of this investigation are compared to his experimental results in order to emphasize the pre- dictive and elucidative power of molecular dynamics (MD) simulations. 2. Experimental The experimental method used by Thompson has been extensively described elsewhere [1–3] and, therefore, is only briefly explained here. A pulsed mass-separated 20 keV argon ion beam is used to bombard a radioactive gold (1 0 0) crystal along the [1 1 0] direction 458 from surface normal. A fraction of the sputtered atoms travel through a collimator down a flight path to a spinning cylinder while a majority of the sputtered atoms impinge the static Applied Surface Science 231–232 (2004) 39–43 * Corresponding author. Tel.: þ1-814-865-0493; fax: þ1-814-863-0618. E-mail address: cmm336@psu.edu (C.M. McQuaw). 0169-4332/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2004.03.021