Single collision focusing and the angular distribution of sputtering from Zr(0001)

The role of single collision momentum focusing in direct ejection sequences leading to sputtering of atoms from Zr(0001) by 1.5 keV Ar at normal incid ence has been investigated using a molecular dynamics simulation. Collision s have been assigned in the simulations and collision sequences leading to sputtering have been classified. The features of the angular distribution o btained for direct ejection sequences are inconsistent with a simple view o f single collision momentum focusing in direct ejection sequences. The angu lar distribution of sputtering is determined more by blocking of exit traje ctories of ejecting surface atoms by their nearest neighbors in the surface . (C) 1999 Elsevier Science B.V. All rights reserved.