MD simulation of cluster formation during sputtering

Abstract

The cluster ejection due to cluster impact on a solid surface is studied through molecular dynamics (MD) simulations. Simulations are performed for Cu cluster impacts on the Cu(1 1 1) surface for cluster energy 100 eV/atom, and for clusters of 6, 13, 28 and 55 atoms. Interatomic interactions are described by the AMLJ–EAM potential. The vibration energy spectrum is independent of the incident cluster size and energy. This comes from the fact that sputtered clusters become stable through the successive fragmentation of nascent large sputtered clusters. The vibration energy spectra for large sputtered clusters have a peak, whose energy corresponds to the melting temperature of Cu. The exponent of the power-law fit of the abundance distribution and the total sputtering yield for the cluster impacts are higher than that for the monatomic ion impacts with the same total energy, where the exponent δ is given by Y n ∝ n δ and Y n is the yield of sputtered n-atom cluster. The exponent δ follows a unified function of the total sputtering yield, which is a monotonic increase function, and it is nearly equal to δ ∼ −3 for larger yield.