Pt(111)表面低能溅射现象的分子动力学模拟

利用嵌入原子方法的原子间相互作用势，通过分子动力学模拟，详细研究了贵金属原子在Pt (111)表面的低能溅射现象.模拟结果显示：对于垂直入射情况，入射原子的质量对Pt (11 1)表面的溅射阈值影响不大.当入射原子的能量小于溅射阈值时，入射原子基本以沉积为主 ；当入射原子的能量大于溅射阈值时，溅射产额随入射原子能量的增加而线性增大；当入射 原子能量达到200 eV时，各种入射原子的溅射产额都达到或接近1，此时入射原子主要起溅 射作用.溅射原子发射的角分布概率和溅射花样与高能溅射相类似.研究表明：与基于二体碰 撞近似的线性级联溅射理论不同，当入射原子能量大于溅射阈值时，低能入射原子的溅射产 额正比于入射原子的约化能量和入射原子与基体原子的质量比.通过对低能入射原子的钉扎 能力分析，提出了支配低能溅射的入射原子反射物理机理. 关键词： 分子动力学模拟、低能溅射

Study of low energy sputtering of Pt(111) surface by molecular dynamics simulation

Low energy sputtering of Pt (111) surface by noble metal atoms with the incident energy in the range of 0.1 — 200 eV has been studied by molecular dynamics sim ulation. The atomic interaction potential with embedded atom method (EAM) was us ed in the simulation. It was found that the sputtering threshold energy is indep endent of the mass of the incident atom in the case of normal impact on the Pt ( 111) surface. When the incident energy is lower than the threshold energy, the b ehavior of incident atom can be regarded as deposition process. When the inciden t energy is higher than the threshold energy, however, the sputtering yield incr eases with the increase of the incident energy. For the incident energy of 200 e V, the sputtering yield induced by various incident atoms approaches 1 or even h igher. The results mean that the atom with incident energy higher than 200 eV ma inly plays the role of sputtering. The probability of angular distribution of th e sputtered atoms and the sputtering pattern are similar to the sputtering resul ts with higher incident energy. We found that the sputtering yield is a function of the reduced energy of incident atom and the mass ratio of incident atom to t arget atom when the incident energy is higher than the threshold energy, which i s different from the linear cascade theory based on the binary collision model. We suggest a new physical mechanism for low energy sputtering, where the reflect ion of incident atom by target atom dominates the sputtering process of surface atoms.