Nonlinear Phenomena in Cluster Ion impact on Solid Surfaces

研究了团簇离子与固体表面的相互作用，即所谓的“非线性现象”。分子动力学计算表明，团簇离子碰撞过程与单体离子碰撞过程相差甚远，而单体离子碰撞过程可用二元碰撞理论来描述。在飞秒时间尺度内，许多原子撞击小的表面区域。因此，一个新的相互作用的团簇组成原子与表面原子的每次碰撞是预期的。在本研究中使用的平均团簇大小约为3000通过使用飞行时间（TOF）技术。由于重离子二次电子发射效率小于1。为了精确测量团簇离子的尺寸分布，我们对效率进行了仔细的标定。在飞行时间谱中不仅发现了单电荷团簇离子，而且发现了多电荷团簇离子。已经报道了团簇离子撞击形成的陨石坑。我们发现形成陨石坑的最小尺寸是10。这一结果也得到了分子动力学计算的证实。为了实现团簇离子西姆斯，研究了团簇离子的二次离子发射。用Sb掺杂的硅样品测量了Ar团簇离子作为主离子的西姆斯谱。二次离子发射产额与溅射产额成正比。这表明团簇离子在实现高深度分辨西姆斯方面具有很大的优势。团簇离子对固体表面独特的轰击效应使溅射表面平整化、浅注入和二次离子发射的产率都很高。

Interaction between cluster ions and solid surfaces, which is the so-called "nonlinear phenomena", has been studied. Molecular dynamics calculation shows that cluster ion impact process is far from monomer ion impact process, which is well described with binary collision theory. Many atoms impact on small surface area within femto-second time scale. Therefore, a new interaction of each collision of the cluster constituent atoms with the surface atoms is expected.Average cluster size used in this study was about 3000 by using Time of fight (TOF) technique. Detection efficiency of multi channel plate (MCP) should be considered because secondary electron emission efficiency of heavy ion was less than 1. We have calibrated the efficiency carefully in order to measure the size distribution of cluster ion precisely. Not only singly charged cluster ions but also multiple-charged cluster ions were found in the TOF spectra. Crater formation with cluster ion impact has been reported. We have found that the minimum size for crater formation is 10. This result was also confirmed by MD calculation. Secondary ion emission was studied in order to realize cluster ion SIMS. Sb doped silicon was used to measure the SIMS spectra with Ar cluster ions as primary ions. Secondary ion emission yield is proportional to the sputtering yield. This indicates that cluster ion has a great advantage to realize high-depth resolution SIMS. These unique bombardment effects of cluster ions on solid surfaces cause high yield of sputtering surface smoothing, shallow implantation and high yield of secondary ion emission.