Ag/Cu(111)与Au/Cu(111)体系异质外延岛演化过程中的应变释放及其对Moiré结构形成的影响

采用嵌入原子方法的原子间相互作用势，利用分子动力学模拟方法研究了Au/Cu(111)和Ag/Cu (111)体系的异质外延结构特征以及外延岛形貌和应变释放的演化过程. 通过对比Au/Cu(111)和Ag/Cu (111)体系的异质外延结构及外延岛演化行为，揭示了导致Ag/Cu (111)体系中异质外延层形成Moiré结构的微观物理机理及其与外延体系的宏观物理特性之间的关系. 研究结果显示，外延岛原子与基体表面原子之间的界面结合强度是形成Moiré结构的重要因素，异质外延体系的界面结合强度取决于二者的合金熔解热. 当异质外延体系的合金熔解热为正值时，界面结合强度较弱，有利于Moiré结构的形成. 同时，外延岛原子之间的相互作用决定着外延岛的面内弛豫行为，对Moiré结构的形成有一定的影响. 外延岛的面内弛豫行为与外延层和基体之间的相对刚度有关，弹性模量较大的外延层具有较强的延展能力，对Moiré结构的形成有利. 此外，Moiré结构的形成与外延岛的尺度有关，主要是外延岛边界原子的钉扎作用对外延岛内原子弛豫行为的约束作用的影响.

Strain relaxation in heteroepitaxial islands of Au/Cu(111) and Ag/Cu(111) systems and its effects on the formation of Moiré structure

Molecular dynamics simulation was used to study the strain relaxation and evolution of Ag/Cu(111) and Au/Cu(111) heteroepitaxial systems with embedded atom method. By comparing the evolution behaviors of the two systems, the atomistic mechanism leading to the formation of Moir structure in Ag/Cu(111) epitaxial layer is studied and is related to the physical properties of the components in the heteroepitaxial system. It is found that the adhesion between epilayer and substrate is one of the important factors that affect the formation of Moir structure. Positive solution heat of the alloy enables the adhesion of heteroepitaxial system to be weak and is helpful for the formation of Moir structure. The relaxing ability of atoms in epilayer is also important in the formation of Moir structure, which can be related to the bulk modulus of epilayer. The larger the bulk modulus of epilayer, the easier the formation of Moir structure. On the other hand, the formation of Moir structure is related to the island size, which is caused by the boundary atoms confining the relaxation of interior atoms in the island.