Numerical simulations of stress generation and evolution in Volmer–Weber thin films
Numerical simulations of stress generation and evolution in Volmer–Weber thin films
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DOI：
10.1016/j.jmps.2008.02.008
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发表时间：
2008-08
影响因子：
5.3
通讯作者：
J. Tello;A. Bower
中科院分区：
文献类型：
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作者：
J. Tello;A. Bower
我们提出了一个详细的模型的应力和形状的变化，发生在多晶薄膜在Volmer-Weber生长。我们的模型跟踪了一系列岛屿的形状，因为它们生长并合并成一个连续的薄膜。由于沉积通量以及表面和晶界扩散，岛改变形状。当相邻岛相遇形成晶界时，由于在相邻岛之间施加的力而在膜中产生应力。岛的内应力和扩散的变化，它们的表面和晶界上的计算使用耦合有限元方案。相邻岛屿之间的相互作用建模使用内聚区法。我们的模型预测的应力-厚度与厚度的行为，是非常符合实验。具体来说，我们观察到一个三阶段的增长过程，包括一个无应力的预聚结阶段，在聚结的快速拉伸上升，并最终过渡到一个稳定的状态。稳态应力可以是拉伸的或压缩的，这取决于沉积速率、晶粒尺寸和膜的性质。进行详细的参数研究，以建立材料特性和生长条件对应力历史的影响，并将结果与实验观察和以前的模型进行比较。
We present a detailed model of the stresses and shape changes that occur in polycrystalline thin films during Volmer–Weber growth. Our model tracks the shape of an array of islands as they grow and coalesce into a continuous film. The islands change shape as a result of the deposition flux, as well as surface and grain boundary diffusion. Stress is generated in the film as a result of forces exerted between neighboring islands as they meet to form a grain boundary. The internal stresses in the islands and the diffusive changes on their surfaces and grain boundaries are computed using a coupled finite element scheme. Interactions between neighboring islands are modeled using a cohesive zone law. Our model predicts stress-thickness vs. thickness behavior that is in excellent agreement with experiments. Specifically, we observe a three-stage growth process consisting of a stress-free pre-coalescence stage, a rapid tensile rise at coalescence, and an eventual transition to a steady-state. The steady-state stress may be tensile or compressive, depending on the deposition rate, the grain size, and the properties of the film. Detailed parametric studies are conducted to establish the influence of material properties and growth conditions on the stress history, and the results are compared with experimental observations and previous models.