Computer studies on reflection and sputtering due to low-energy cluster impacts

In order to study the reflection and sputtering by low-energy cluster impac t, we have performed the molecular dynamics (MD) simulations of (CU)(55) cl uster impact on a Pt (111) surface with an energy of 100 eV/atom, and compa red with those of monatomic Cu ion bombardment with the same energy per ato m. As to the reflection, the lower-part cluster atoms are more reflected th an the upper-part cluster atoms at the very-early stage of cluster impact. This is the high-density effect on the reflection by cluster impact. Howeve r, the upper-part cluster atoms are more reflected than the lower-part clus ter atoms after all. As to the sputtering, the sputtering yield for cluster impact is by far larger than that for monatomic ion bombardment. In the ca se of monatomic ion bombardment, Pt atoms tend to be sputtered in the close -packed directions of the Pt (111) target. In the case of cluster impact, P t atoms are fairly sputtered in the normal and lateral directions as well a s the close-packed directions. These results for sputtering agree with expe rimental observations and other simulation results. The sputtering in the n ormal and lateral directions is certainly enhanced due to cluster impact, b ut the high-density effect on the sputtering by cluster impact is not clear ly observed. The high-density effect is not the main effect on the reflecti on and sputtering by cluster impact, and it does not seem to be observable experimentally. (C) 1999 Elsevier Science B.V. All rights reserved.