Computer Studies of Culster Implantation

为了研究电离团簇束与固体的团簇注入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。DYACOCT代码可用于研究结晶固体中的团簇撞击现象。在这个基于二元碰撞近似的程序中，离子和反冲原子的轨迹被动态跟踪。利用分子动力学技术对通道粒子的多次碰撞效应进行了精确估计。为了克服低能弹丸二元碰撞近似的困难，还采用分子动力学方法对弹丸与其碰撞直径内的多个原子同时碰撞的多体碰撞进行了数值求解。这些代码可以成功地应用于模拟辐射损伤、团簇撞击现象、高电荷粒子与固体表面的相互作用以及团簇撞击引起的溅射。为了确定簇束对深度分布的簇效应，必须知道离子注入引起的深度分布。为此，我们使用了（110）平面通道和<110>轴向通道的Si晶体，通过类marlow代码（ACOCT代码）计算了注入离子的深度分布。我们使用As^+离子作为注入剂，因为簇离子的清路效应被认为在As- si结合中得到增强。对于（100）Si表面上的1.06 MeV As^+和（110）Si表面上的20 keVAs^+，计算的深度剖面都有两个峰，即随机峰和通道峰。前一个通道峰是平面通道，后一个通道峰是轴向通道。利用DYACOCT代码对簇状植入进行了研究。20 keV/原子（As）_n （n bbb10）在（110）Si表面正常轰击后的模拟深度分布有两个有趣的特征：随机峰比单离子注入时的深度峰向更深的层移动。第二个有趣的特征是轴向通道峰值被强烈地推断出来。由于这种组合的M_<21>M_1小于1，因此许多Si原子的速度比入射的As原子的速度大，为后面的簇原子扫清了道路，并在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