| Research Abstract |
In order to investigate the basic processes of the cluster implantation interaction of an ionized cluster beam with solids, we have developed the time-evolution Monte Carlo simulation codes DYACAT and the molecular dynamics code MDACOCT.In order to clarify the cluster effect on the cluster implantation, we calculated the depth profiles and its projected range in the wide energy range. We used the DYACAT and MDACOCT for E> 100 eV and for E<lO0eV, respectively, in order to calculated the depth profiles due to cluster and monatomic ion impact. The ratios of cluster-impact range to the monatomic ion range are larger than unity due to the clear-the-way effect. For the very high-energy (>5 kev/atom) the ratio become less than unity due to the cluster-enhanced-randomization. In the case of E < 30 eV the ratios by the DYACAT is less than those by the MDACOCT because of the many body effect. The present simulation says that there are important three cluster effects, i.e., many-body effect, clea
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r-the-way effect and cluster-enhanced-randomization, for the cluster implantation.
The mechanism of thin-film growth by ionized cluster beam deposition has been investigated, using molecular dynamics simulation code MDACOCT with the hybrid interatomic potentials which have been developed by combining embedded-atom potentials with the screened Coulomb potential. In order to clarify the conversion mechanism of cluster energy into surface migration energy, we have simulated the cluster-impact-phenomena for Cu_<201> on Cu(111) and Pt(111) with the cluster energy 5eV/atom. For the latter case, a half of cluster atoms migrated on the substrate surface with the relatively high energy and for the former case most of the cluster atoms are embedded into the substrate. In the conversion mechanism the most important point is when the high-density zone in the cluster is formed in the central part of the cluster, i.e., above or below the surface.
When the cluster is bombarded on the surface, the high-density zone is always produced in the cluster. This high-density effect on the angular distribution of penetrating cluster atoms has been studied by the MDACOCT for Cu_<201> impact on Pt(111) and Pt_<201> impact on Cu(111), where the cluster energies are changed from 5eV to 50 keV.It is found the high-density formation is strongly dependent on the cluster energy and the mass ratio between cluster atom and target atom and that the angular distributions of cluster atoms are enhanced near the lateral direction for low-energy cluster impact due to the high-density formation. Less
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