Cluster ion
The depth profile and energy dependence of big cluster impacts on amorphous targets have been investigated by using the time-evolution Monte Carlo simulation code DYACAT, where we used three different combinations of 200 eV/atom (Ag)n cluster impacts on Al, 400 eV/atom (Al)n cluster on Ag, and 200 eV/atom (D)n cluster on Ag (nbeing 1 to 500).
In the case of (Ag)n cluster impact on an Al target, where the atomic mass of the cluster atom is larger than that of the target atom, the recoil atoms clear the way for the afetercoming cluster. The projected range of a (Ag)500 cluster is about four times larger than that for monoatomic ion bombardment. In the case of (Al)n cluster impact on a Ag target, where the atomic mass of the Al atom is less than that of the target Ag atom, the clear-the-way effect is not so large if n < 100. In this case the over-runners are the constituent Al atoms in the lower part of the cluster. In the case of a (D)n cluster impact on a Ag target, where the atomic mass of deuterium is much less than that of Ag, there is no clear-the-way effect. The projected range of big (D)n clusters is less than that for monoatomic ion bombardment due to the enhanced energy removal from the surface.
Concerning the energy dependence of the impact region, the big cluster impact produces a quasi-equilibrium state after a certain time which depends on the cluster-target combination. The acceleration effect of the constituent atom is roughly estimated by the Fermi-shuttle process, and that of the recoil atom is discussed using the simple collision sequence.
