Computer Simulation 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DYACAT和分子动力学程序MDACOCT。为了阐明团簇效应对团簇注入的影响，我们在较宽的能量范围内计算了团簇注入的深度分布及其投影范围。我们使用DYACAT和MDACOCT分别对E&gt；100 eV和E&lt；100 eV进行了计算，以计算团簇离子和单原子离子碰撞引起的深度分布。由于遮挡效应，团簇撞击范围与单原子离子范围之比大于1。对于很高的能量(~gt；5keV/原子)，由于团簇增强的随机化，这一比率变得不到1。在E&lt；30EV的情况下，由于多体效应，DYACAT的比率小于MDACOCT的比率。目前的模拟表明，有三个重要的团簇效应，即多体效应，Clea…利用分子动力学模拟程序MDACOCT，结合嵌入原子势和屏蔽库仑势，研究了电离团束沉积薄膜的生长机理。为了阐明团簇能量转化为表面迁移能的机制，我们用团簇能量为5 eV/原子的方法模拟了Cu201&gt；在Cu(111)和Pt(111)面上的团簇碰撞现象。对于后一种情况，一半的团簇原子以较高的能量迁移到衬底表面，而对于前一种情况，大多数团簇原子嵌入到衬底中。在转化机制中，最重要的一点是团簇中的高密度区在团簇的中心部分，即表面上方或下方形成，当团簇被轰击到表面时，团簇中总是产生高密度区。研究了这种高密度效应对穿透团簇原子角分布的影响。在团簇能量从5 eV到50keV的情况下，用MDACOCT方法研究了穿透团簇原子对铂(111)和铂(111)的影响。结果表明，高密度的形成强烈依赖于团簇的能量和团簇原子与靶原子的质量比，对于低能团簇碰撞，由于高密度的形成，团簇原子的角分布在横向附近得到增强。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 DYACAT and the molecular dynamics code MDACOCT.In order to clarify the cluster effect on the cluster implantation, we calculated the depth profiles and its projected range in the wide energy range. We used the DYACAT and MDACOCT for E> 100 eV and for E<lO0eV, respectively, in order to calculated the depth profiles due to cluster and monatomic ion impact. The ratios of cluster-impact range to the monatomic ion range are larger than unity due to the clear-the-way effect. For the very high-energy (>5 kev/atom) the ratio become less than unity due to the cluster-enhanced-randomization. In the case of E < 30 eV the ratios by the DYACAT is less than those by the MDACOCT because of the many body effect. The present simulation says that there are important three cluster effects, i.e., many-body effect, clea … More r-the-way effect and cluster-enhanced-randomization, for the cluster implantation.The mechanism of thin-film growth by ionized cluster beam deposition has been investigated, using molecular dynamics simulation code MDACOCT with the hybrid interatomic potentials which have been developed by combining embedded-atom potentials with the screened Coulomb potential. In order to clarify the conversion mechanism of cluster energy into surface migration energy, we have simulated the cluster-impact-phenomena for Cu_<201> on Cu(111) and Pt(111) with the cluster energy 5eV/atom. For the latter case, a half of cluster atoms migrated on the substrate surface with the relatively high energy and for the former case most of the cluster atoms are embedded into the substrate. In the conversion mechanism the most important point is when the high-density zone in the cluster is formed in the central part of the cluster, i.e., above or below the surface.When the cluster is bombarded on the surface, the high-density zone is always produced in the cluster. This high-density effect on the angular distribution of penetrating cluster atoms has been studied by the MDACOCT for Cu_<201> impact on Pt(111) and Pt_<201> impact on Cu(111), where the cluster energies are changed from 5eV to 50 keV.It is found the high-density formation is strongly dependent on the cluster energy and the mass ratio between cluster atom and target atom and that the angular distributions of cluster atoms are enhanced near the lateral direction for low-energy cluster impact due to the high-density formation. Less