The ground-breaking properties of biaxially textured thin films have attracted increasing attention to the characterization and growth theory of their crystal morphologies. In particular, multi-faceted columnar structures developed during oblique angle deposition (OAD) show abnormal tilt angles that have not been previously captured by existing models. Current theories for the formation of biaxially aligned columnar structures overlook the fact that the surface diffusion on individual facets can be finite. In this work, a continuum model incorporating finite adatom mobility, flux-dependent sticking coefficient, and material-specific surface energies is employed to study the growth of a well-known MgO-OAD system. Experimentally observed morphologies are reproduced by simulating the shadowing growth of an array of preferentially oriented single crystals. We show that the abnormal tilting is elusive considering only the effects of faceting and shadowing. A proposed sticking coefficient in our model, determined by the component of adatom momentum parallel to the surface, is responsible for the development of abnormal tilting. The role of faceting is demonstrated by its effect on the resulting columnar morphologies. Using the proposed model, the characteristic morphology and tilting behavior of a CaF 2-OAD system are also obtained, which agree with experiments.

中文翻译：

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刻面在双轴织构薄膜中的作用：柱状形态和异常倾斜

双轴织构薄膜的突破性特性引起了对其晶体形态表征和生长理论的越来越多的关注。特别是，在斜角沉积 (OAD) 过程中形成的多面柱状结构显示出异常的倾斜角，这是现有模型以前未捕获的。目前形成双轴排列的柱状结构的理论忽略了单个小平面上的表面扩散可能是有限的这一事实。在这项工作中，采用包含有限吸附原子迁移率、通量相关粘附系数和材料特定表面能的连续模型来研究众所周知的 MgO-OAD 系统的生长。通过模拟一系列优先取向的单晶的阴影生长，可以重现实验观察到的形态。我们表明，仅考虑刻面和阴影的影响，异常倾斜是难以捉摸的。我们模型中建议的粘附系数由平行于表面的吸附原子动量分量确定，是导致异常倾斜的原因。刻面的作用通过其对所得柱状形态的影响得到证明。使用所提出的模型，还获得了 CaF 2-OAD 系统的特征形态和倾斜行为，这与实验一致。由平行于表面的吸附原子动量分量决定，负责异常倾斜的发展。刻面的作用通过其对所得柱状形态的影响得到证明。使用所提出的模型，还获得了 CaF 2-OAD 系统的特征形态和倾斜行为，这与实验一致。由平行于表面的吸附原子动量分量决定，负责异常倾斜的发展。刻面的作用通过其对所得柱状形态的影响得到证明。使用所提出的模型，还获得了 CaF 2-OAD 系统的特征形态和倾斜行为，这与实验一致。