Computer Studies on Interactions of Ionized Cluster Beam With Solids

为了研究离化团簇束与固体的相互作用，我们开发了时间演化蒙特卡罗模拟程序DYACOCT^<1）>和DYACAT^<2）>。DYACAT程序适用于非晶态固体中团簇碰撞现象的研究，DYACOST程序适用于晶态固体中团簇碰撞现象的研究。在这些程序中，这是基于二元碰撞近似，离子和反冲原子的轨迹动态跟踪。为了克服低能射弹二元碰撞近似的困难，采用分子动力学方法数值求解了多体碰撞问题，即一个射弹同时与其碰撞直径内的多个原子碰撞。为了研究低能团簇碰撞现象，对电离的（Ag）_n团簇束（n = 100 t）进行了数值模拟，结果表明：（Ag）_n团簇束的能量密度为100 t/s时，（Ag）_n团簇束的能量密度为100 ...更多信息 500）轰击在无定形碳表面上。研究了电离团簇碰撞现象的能量依赖性和尺寸依赖性。将离子化的Ag团簇束轰击在非晶碳表面。研究发现，离子化团簇束沉积（ICBD）的机理可分为三个阶段：即离子束沉积阶段和离子束沉积阶段。例如，高表面密度的形成、高表面密度的反射以及由于团簇上部的原始原子与来自致密表面的反射原子之间的碰撞而导致的团簇中的碰撞尖峰。因此，在具有几个eV/原子的能量的团簇束的情况下，多体效应是必不可少的，并且轰击能量被转换为表面迁移能量。为了研究团簇的高能碰撞现象，用能量为几keV/atom的（Ag）n和（Al）n团簇离子束（n = 100 ~ 500）分别轰击非晶碳和金靶。结果表明，团簇中原子间的相互作用是高能团簇碰撞现象的重要影响因素之一，在能量为keV/atom的情况下，团簇碰撞现象与团簇的质量比M_1/M_2有很大关系。当M_1 < M_2时，某些组分原子被加速到比入射能量/原子大三倍的能量。团簇碰撞现象中最重要的效应之一是团簇中组成原子之间的相互作用。少

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