Strain in metal(100) heteroepitaxial thin-film growth can lead to a variety of effects such as the formation of stacking faults (SFs). To gain a better understanding we have carried out temperature-accelerated dynamics (TAD) simulations of the submonolayer growth of Cu islands on a biaxially strained Cu substrate at 200 K. In the case of 4% compressive strain we find that SF formation occurs with a morphology very similar to the structures found experimentally in Cu/Ni(100) growth. We also find that islands play a key role by lowering the barrier for vacancy formation. In particular, once two substrate vacancies are formed and diffuse to form the appropriate configuration this leads to the formation of a SF in both the substrate and island. While the activation barrier for SF formation is very high, due to the presence of a large number of low-frequency vibrational modes, the saddle-point entropy is large while the corresponding Vineyard prefactor is more than 10 orders of magnitude larger than is typical of atomic processes in fcc metals. Similarly, an analysis of the entropy of the SF state indicates that the reverse prefactor is much smaller, while the free energy of this state is lower than that of the initial state.

中文翻译：

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金属（100）异质外延生长中堆垛层错形成的机理

金属（100）外延外延薄膜生长中的应变会导致多种影响，例如堆垛层错（SFs）的形成。为了更好地理解，我们对温度为200 K的双轴应变Cu基板上Cu岛的亚单层生长进行了温度加速动力学（TAD）模拟。在4％压缩应变的情况下，发现在形态与在Cu / Ni（100）生长中实验发现的结构非常相似。我们还发现，岛屿通过降低空缺形成的障碍发挥了关键作用。特别地，一旦形成两个衬底空位并扩散以形成适当的构造，这将导致在衬底和岛中均形成SF。尽管SF形成的激活障碍非常高，由于存在大量低频振动模式，因此鞍点熵很大，而对应的葡萄园前置因子要比fcc金属中原子过程的典型因子大10个数量级。类似地，对SF状态的熵的分析表明，反向预因子要小得多，而该状态的自由能低于初始状态的自由能。