Computer Studies on Interactions of Ionized Cluster Beam With Solids

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In order to investigate the interaction of an ionized cluster beam with solids, we have developed the time-evolution Monte Carlo simulation codes DYACOCT^<1)> and DYACAT^<2)>. The DYACAT code can be applied to the investigation of the cluster-impact phenomenon in an amorphous solid, and the DYACOST code to that in a crystalline solid. In these programs which are based on the binary collision approximation, trajectories of ions and recoil atoms are followed dynamically. In order to overcome the difficulties of the binary collision approximation of a low-energy projectile, many body encounter are numerically solved by the molecular dynamics method, where a projectile collides at the same time with many atoms within its collision diameter. These codes can be successfully applied to the sputtering phenomena^<3)>, radiation damage^<4,5)> and the cluster-impact phenomena^<,2,6,7)>.In order to investigate the low-energy cluster-impact phenomenon, the ionized (Ag)_n cluster beam (n being 100 t … More o 500) with energies of a few eV/atom are bombarded on an amorphous carbon surface. The energy-dependencies and the size dependencies of the ionized cluster impact phenomena have been studied. The ionized Ag cluster beam are bombarded on amorphous carbon surface. It is found that the mechanism of ionized cluster beam deposition (ICBD) can be divided into three stages, i. e., high surface density formation, reflection by the high surface density and collisional spike in the cluster due to the collision between virgin atoms in the upper part of cluster and reflected atoms from the dense surface. Thus, in the case of a cluster beam with energy of a few eV/atom the many body effect is essential and the bombarding energy is converted to the surface migration energy. Another important conclusion is that the larger cluster has the higher ICBD efficiency if the incident energy per atom is enough small.In order to investigate the high-energy cluster-impact phenomenon, the ionized (Ag)n and (Al)n cluster beam (n being 100 to 500) with energies of a few keV/atom are bombarded on amorphous carbon and gold targets, respectively. It is found that one of most important effects in the high-energy cluster-impact phenomena is the interaction between the constituent atoms in the cluster and that in the case of a cluster beam with energy of keV/atom the cluster-impact phenomena depends so much on the mass ratio M_1/M_2. when M_1 < M_2, some constituent atoms are accelerated up to three times larger energies than the incident energy/atom. One of the most important effects in the cluster-impact phenomena is the interaction between the constituent atoms in the cluster. Less