Computer Studies of Culster Implantation

为了研究离化团簇束与固体相互作用的基本过程，我们开发了时间演化蒙特卡罗模拟程序DYACOCT，该程序可用于研究团簇与固体的碰撞现象。该程序基于二元碰撞近似，对离子和反冲原子的运动轨迹进行了动态跟踪。用分子动力学方法对沟道粒子的多次碰撞效应进行了精确的估计。为了克服低能射弹的二元碰撞近似的困难，还用分子动力学方法数值求解了多体碰撞，其中射弹同时与其碰撞直径内的多个原子碰撞。这些程序可以成功地应用于辐射损伤、团簇碰撞现象、高电荷粒子相互作用的模拟 关于我们 为了明确团簇束对深度分布的团簇效应，必须知道离子注入引起的深度分布。为此，我们采用了类似MARLOWE的ACOCT程序计算了注入离子的深度分布，其中考虑了Si晶体的（110）面沟道和<110>轴沟道。我们使用As^+离子作为簇离子，因为簇离子的开路效应被认为对于As-Si组合是增强的。对于（100）Si表面上的1.06 MeV As^+和（110）Si表面上的20 keV As ^+，计算的深度分布都有两个峰值，即，随机峰和沟道峰。用DYACOCT程序研究了团簇注入过程中的沟道效应。20 keV/atom（As）_n（n&gt;10）垂直轰击（110）Si表面的模拟深度分布有两个有趣的特点：与单次离子注入相比，无规峰向深层移动。第二个有趣的特点是，强烈推导出轴向沟道峰。由于M_<21>M_1小于1，所以大量Si原子的速度比入射As原子的速度大，它们为后面的团簇原子扫清了道路，在团簇原子到来之前破坏了通道。少

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 DYACOCT.The DYACOCT code can be applied to the investigation of the cluster-impact phenomenon in a crystalline solid. In this program which is based on the binary collision approximation, trajectories of ions and recoil atoms are follwed dynamically. The effect of the multiple collisions of channeling particles is estimated precisely by the Molecular dynamic technique. In order to overcome the difficulties of the binary collision approximation of a low-energy projectile, many body encounter are also 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 simulations of the radiation damage, the cluster-impact phenomena, the interaction of a highly charged particles … More with the solid surface and sputtering due to cluster impacts.In order to specify the cluster effect of the cluster beam on the depth profile, It is necessary to know the depth profiles due to the ion implantation. For this purpose, the depth profiles of implanted ions has been calculated by the MARLOWE-like code, ACOCT code, where we used the (110) planar channeling and the <110> axial channeling of Si crystal. As an implantedion we used As^+ ion, because the clear-the-way effect of cluster ions is considered to be enhanced for the As-Si combination. For both 1.06 MeV As^+ on (100) Si surface and 20 keVAs^+ on (110) Si surface the calculated depth profile have two peaks, i.e., the random peak and the channeling peak. The former channeling peak is due to the planar channeling and the latter due to the axial channeling.The cluster implantation was investigated by the DYACOCT code. The simulated depth profile due to 20 keV/atom (As)_n (n>10) bombarded normally on (110) Si surface has two interesting features : The random peak is shifted to the deeper layr than that of a single ion implantation. The second interesting feature is that the axial channeling peak is strongly deduced. Since M_<21>M_1 is less than unity for this combination, a lot of Si atoms have larger velocities than incident As atoms, and they clear the way for aftercoming cluster atoms, and they destroy the channel before cluster atoms come. Less