Abstract The evolution of internal stress in ultrathin amorphous carbon (a-C) films is a complex physical process that is difficult to experimentally analyze due to the very small film thickness (a few nanometers) and the lack of instruments that can perform spatiotemporal stress measurements at sub-nanometer resolutions. Even more challenging is the elucidation of the correlation between internal stress, film structure, and temperature. Molecular dynamics (MD) provides potent computational capability for tracking structural changes triggered by stress and temperature at the atomic level. Consequently, the aim of this study was to perform a comprehensive MD analysis that elucidates the origin of internal stress in sub-2-nm-thick a-C films grown on single-crystal silicon under optimal deposition energy conditions and explore its dependence on prevalent structural features (e.g., hybridization state) and temperature. The physical mechanisms of a-C film growth and stress built-up under deposition conditions of energetic particle bombardment and stress relief due to thermal annealing are interpreted in the context of MD results. Simulations of film growth illuminate the correlation between film stress and energy of incident carbon atoms. A significant stress relief occurs mainly in the bulk layer of the multilayered a-C film structure at a critical annealing temperature, which continues to intensify with the further increase of temperature. Simulations of time-dependent variation of stress through the film thickness reveal that the stress relief is a very fast process that accelerates with the increase of temperature. The results of this study provide insight into the spatial and temporal variation of internal stress in ultrathin a-C films due to structure and temperature effects and the film stress-structure interdependence.

中文翻译：

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超薄非晶碳薄膜热退火内应力演化的分子动力学模拟

摘要 超薄非晶碳 (aC) 薄膜中内应力的演变是一个复杂的物理过程，由于薄膜厚度非常小（几纳米），并且缺乏可以在亚低温下进行时空应力测量的仪器，因此难以通过实验进行分析。 - 纳米分辨率。更具挑战性的是阐明内应力、薄膜结构和温度之间的相关性。分子动力学 (MD) 提供了强大的计算能力，可以在原子水平上跟踪由应力和温度引发的结构变化。最后，本研究的目的是进行全面的 MD 分析，阐明在最佳沉积能量条件下在单晶硅上生长的亚 2 纳米厚 aC 薄膜中的内应力起源，并探索其对普遍结构特征（例如，杂交状态）和温度。在高能粒子轰击沉积条件下以及由于热退火引起的应力消除的 aC 膜生长和应力积累的物理机制在 MD 结果的背景下进行解释。薄膜生长的模拟阐明了薄膜应力与入射碳原子能量之间的相关性。在临界退火温度下，显着的应力消除主要发生在多层 aC 膜结构的体层中，并且随着温度的进一步升高而继续加剧。通过薄膜厚度的应力随时间变化的模拟表明，应力消除是一个非常快速的过程，随着温度的升高而加速。这项研究的结果提供了对超薄 aC 薄膜中由于结构和温度效应以及薄膜应力-结构相互依赖性而导致的内应力的空间和时间变化的深入了解。