Au/Cu(001)异质外延岛演化的分子动力学研究

利用分子动力学弛豫方法模拟了Au/Cu(001)异质外延生长初期Au异质外延岛的形貌演化，分析了Au外延岛演化过程中的局域应力及与基体结合能随表面岛尺寸的变化. 研究结果表明：当异质外延岛小于7×7时，外延岛原子分布呈现赝Cu点阵形貌；当外延岛达到8×8后，外延岛内开始出现失配位错，失配位错数量随外延岛尺寸的增加而增加. 局域压力分析指出，外延岛上原子之间的近邻环境不同导致了所受应力的差异，而外延岛的形变则是由外延岛原子的应力分布所决定. 研究还发现，失配位错的产生导致错位原子与基体原子之间的结合强度减弱，但相对增加了非错位原子与基体原子之间的结合强度. 关键词： 异质外延 表面形貌 局域压力 分子动力学模拟

Study on the evolution of Au heteroepitaxial islands on Cu(001) by molecular dynamics simulation

Molecular dynamics simulation was used to relax the heteroepitaxial Au islands in monolayer on Cu(001) substrate in the initial stage of film growth. The evolution of the morphology and local pressure of the heteroepitaxial Au islands as well as the adhesive energy to the substrate have been analyzed. The simulation results show that a pseudo-morphologically strained Au island is formed when the heteroepitaxial Au island is not larger than 7×7. When the heteroepitaxial Au island is as large as 8×8, however, a misfit dislocation induced by the stress, which results from the mismatch in the interface, appears. The number of the misfit dislocations increases with increasing scale of the heteroepitaxial Au island, and moreover, crossing dislocations and vacancies can be observed in large heteroepitaxial Au islands. The analysis results of the local pressure map show that the difference of the neighborhood results in the difference of the stress of the atoms in the heteroepitaxial Au islands. Furthermore, the psudo-morphologically strained Au islands are the results of the different local pressure of Au atoms in the heteroepitaxial Au islands. On the other hand, we found that the misfit dislocations lead to the decrease of the adhesive energy of the mismatched atoms to the substrate, and the adhesion of other atoms increases relatively.