AbstractTo investigate the size-effect of reactive clusters on sputtering processes, we performed molecular dynamics (MD) simulations of reactive cluster ions with various sizes impacting on solid targets. Various sizes of fluorine clusters, (F2)30, (F2)300 and (F2)3000, were irradiated on a Si(100) target at the same total incident energy of 6 keV. These clusters were irradiated on the same target one after another in order to reproduce real experimental conditions such as the accumulation of fluorine atoms in the target. The MD simulations of sequential cluster impacts enabled to perform various statistical analyses regarding the sputtered particles. The study of cluster size distributions showed that the sputtering process by reactive cluster ion impact has similarity with the emission from quasi-liquid materials excited to hyper-thermal conditions by ion bombardment. However, the major sputtered particles were different with each other; Si for (F2)30 (100 eV/atom), SiF2 for (F2)300 (10 eV/atom), and SiF3 for (F2)3000 (1 eV/atom). At the impact of a large size cluster with low incident energy, a large number of Si-F bondings were generated at the cluster-target interface surface, which enhances formation of volatile SiFx compounds with many fluorine atoms. In contrast, a small cluster with high kinetic energy-per-atom could cause the formation of numerous energetic surface atoms at the near surface region, which could be sputtered without being well fluoridated.
Copper Cluster Size Effect in Methanol Synthesis from CO2
