入射能量对Au/Au(111)薄膜生长影响的分子动力学模拟

Molecular dynamics simulation of the effect of incident energy on the growth of Au/Au(111) thin film

利用分子动力学模拟了Au原子在Au(111)表面低能沉积的动力学过程.采用嵌入原子方法的原子间相互作用势,通过对沉积层原子结构的分析和薄膜表面粗糙度、层覆盖率的计算,研究了沉积粒子能量对薄膜质量的影响及其机制.结果表明:当入射能量Ein<25 eV时,沉积层和基体表层均呈现规则的单晶面心立方(111)表面的排列,沉积原子仅注入到基体最表面两层,随着入射能量的增加,薄膜表面粗糙度降低,薄膜越趋于层状生长,入射能量的增加有利于薄膜的成核和致密化;当Ein 25 eV时,沉积层表面原子结构出现了较为明显的晶界,沉积原子注入到基体表面第三层及以下,随着入射能量的增加,薄膜表面粗糙度增加,沉积层和基体表层原子排列越不规则,载能沉积会降低基体内部的稳定性,导致基体和薄膜内部缺陷的产生,降低薄膜质量.此外,当基体内部某层沉积原子数约等于该层总原子数的一半时,沉积原子将能穿过该层进入到基体内部更深层.

The low-energy bombardment on Au （111） surface by Au atoms is studied by molecular dynamics （MD） simulation. The atomic interaction potential of embedded atom method is used in the simulation. The incident-energy effects on the morphologies and the surface roughness values of the deposited films are observed and summarized. The incident energy （Ein） varies from 0.1 eV to 50 eV. The transition of incident energy dependence occurs when the energy value is about 25 eV. The incident energy of about 25 eV is the sputtering threshold of Au （111） substrate. When the incident energy is lower than 25 eV, no atoms can be implanted into the depth beyond the second layer and all atoms are in face-centered cubic （111） arrangement without dislocation. The surface roughness decreases with the increase of the incident energy. For the case of Ein 〉 25 eV, the deposited atoms reach the third layer. When the number of atoms deposited in a substrate layer reaches about half the total number of atoms in this layer, the deposited atoms could go throgh this laer and enter into a deeper layer in the substrate. Surface roughness increases with the increase of the incident energy, and the energetic deposition can produce defects in both substrate and film.