Zhang Di, Peng Linfa, Li Xiaobo, Yi Peiyun, Lai Xinmin
State Key Laboratory of Mechanical System and Vibration , Shanghai Jiao Tong University , Shanghai 200240 , PR China.
Shanghai Key Laboratory of Digital Manufacture for Thin-Walled Structures , Shanghai Jiao Tong University , Shanghai 200240 , PR China.
J Am Chem Soc. 2020 Feb 5;142(5):2617-2627. doi: 10.1021/jacs.9b12845. Epub 2020 Jan 22.
Nanocrystalline carbon films containing preferentially oriented graphene-based nanocrystals within an amorphous carbon matrix have attracted significant theoretical and experimental interest due to their favorable chemical and physical properties. At present, there are intense efforts to study the grain size and growth orientation of the graphene-based nanocrystals to achieve a controllable growth of nanocrystalline carbon films. However, despite the frequent use of plasma-assisted deposition techniques, the atomistic-scale mechanisms, including the effects of plasma density and energy on the nucleation process and growth orientation of the graphene-based nanocrystals, as well as associated dynamic processes involved in deposition processes, have not yet been thoroughly studied. In this paper, the plasma-assisted growth of nanocrystalline carbon thin films with preferentially oriented nanocrystals was systematically studied by hybrid molecular dynamics-Monte Carlo simulations using a recently developed force field, the charge-implicit ReaxFF. By combining the experimental data with the atomistic simulations, we reveal that plasma ion bombardments, in suitable ranges of energies and densities, allow the highest nucleation density in the nanocrystalline carbon films. Theoretically optimum windows of the plasma energy and density are first presented in the form of crystallization phase diagrams. Furthermore, to investigate the relationship between the growth orientation and the plasma ion energy, simulations of graphene irradiated with Ar ions from different incident angles were also performed. On the basis of the mechanism of "survival of the fittest", we proposed using the critical energy of generating the Stone-Thrower-Wales defects to design the growth orientation of graphite-like nanocrystals by controlling the plasma ion energy.
在非晶碳基体中含有优先取向的基于石墨烯的纳米晶体的纳米晶碳膜，因其良好的化学和物理性质而引起了极大的理论和实验关注。目前，人们正在大力研究基于石墨烯的纳米晶体的晶粒尺寸和生长取向，以实现纳米晶碳膜的可控生长。然而，尽管经常使用等离子体辅助沉积技术，但包括等离子体密度和能量对基于石墨烯的纳米晶体的成核过程和生长取向的影响以及沉积过程中涉及的相关动态过程等原子尺度机制尚未得到充分研究。在本文中，使用最近开发的力场——电荷隐式反应力场（charge-implicit ReaxFF），通过混合分子动力学-蒙特卡罗模拟系统地研究了具有优先取向纳米晶体的纳米晶碳薄膜的等离子体辅助生长。通过将实验数据与原子模拟相结合，我们发现，在合适的能量和密度范围内，等离子体离子轰击可使纳米晶碳膜中的成核密度最高。首次以结晶相图的形式给出了等离子体能量和密度的理论最佳窗口。此外，为了研究生长取向与等离子体离子能量之间的关系，还进行了不同入射角的氩离子辐照石墨烯的模拟。基于“适者生存”机制，我们提出通过控制等离子体离子能量，利用产生斯通-威尔士缺陷的临界能量来设计类石墨纳米晶体的生长取向。
