Computer Studies of Culster Implantation

为了研究电离团簇注入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，DYACOCT可用于研究晶体固体中的团簇碰撞现象。在基于二元碰撞近似的程序中，离子和反冲原子的轨迹是动态跟踪的。用分子动力学技术精确地估计了沟道粒子的多次碰撞效应。为了克服低能弹丸二元碰撞近似的困难，还用分子动力学方法数值求解了多个物体碰撞，即弹丸同时与其碰撞直径内的多个原子发生碰撞。这些程序可以成功地应用于辐射损伤、团簇碰撞现象、高电荷态粒子…相互作用的模拟更多的是与固体表面和团簇作用下的溅射有关。为了确定团簇对深度分布的影响，有必要知道离子注入的深度分布。为此，我们用类Marlowe程序ACOCT计算了注入离子的深度分布，其中我们使用了Si晶体的(110)面沟道和轴向沟道。作为一种注入离子，我们使用了^+离子，因为团簇离子的清除效应被认为对As-Si组合有增强作用。对于1.06 MeV As^+在(100)Si表面和20keVAs^+在(110)Si表面，计算的深度分布都有两个峰，即随机峰和沟道峰。前者的沟道峰是平面沟道，后者是轴向沟道，用DYACOCT程序模拟了团簇注入。模拟的20keV/原子(As)_n(n&gt；10)垂直轰击(110)Si表面的深度分布有两个有趣的特征：与单离子注入相比，随机峰向更深的层移动。第二个有趣的特征是轴向沟道化峰值被强烈地推导出来。由于这种组合的M_1小于1，许多Si原子的入射速度比入射原子的速度大，它们为随后的团簇原子扫清了道路，并在团簇原子到来之前破坏了沟道。较少

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