过渡金属硫族化合物柔性基底体系的模型与应用

Model and applications of transition metal dichalcogenides based compliant substrate epitaxy system

柔性基底体系是晶体外延生长领域于20世纪90年代提出的概念.其核心思想是利用超薄的基底,使其在外延生长时能同时与外延晶膜发生应变,以抵消二者之间的晶格失配,从而减少外延晶膜中的位错,提高晶膜的质量.但是人工制备性能优良的超薄基底往往需要较为复杂的工艺.另一方面,过渡金属硫族化合物由于其层状结构特性和层间较弱的范德瓦耳斯相互作用,是天然的柔性基底.本文介绍近几年来新发展的过渡金属硫族化合物柔性基底体系的模型及应用.以Au-MoS_2作为柔性基底外延生长的原型,结合密度泛函理论、线性弹性理论以及位错理论构建模型,并根据计算结果解释了早先利用透射电子显微镜观测到的Au薄膜在MoS_2上外延生长的相关实验现象.此外,本文还介绍了受到该理论模型启发的相关实验工作,特别是利用Au薄膜分离大面积、单层、高质量MoS_2的技术.最后,讨论了在该领域内值得关注和进一步探索的理论问题.

The concept of compliant substrate epitaxy was first proposed by the scientists engaged in crystal growth in the early 1990s. The core idea is to take advantage of such an ultra-thin substrate that the film and the substrate generate strain together to relieve the lattice mismatch during the epitaxy growth. The quality of the epitaxial film is improved due to the reduction of the mismatch dislocation density. However, the preparation of the artificial ultra-thin substrate with good quality requires rather complicated fabrication process. On the other hand, many transition metal dichalcogenides naturally form the compliant substrates, due to their layered structure and weak van der Waals interlayer interaction.In this paper, we introduce the transition metal dichalcogenides based compliant substrate epitaxy model and relevant applications. Through combining density functional theory, linear elasticity theory and dislocation theory, we introduce the model comprehensively by using the Au-MoS_2 as a prototypical example. And we explain the experimental results of Au growing on MoS_2 from the early transition electron microscopy. In addition, we introduce the experimental work related to the model, especially the Au-mediated exfoliation of large, monolayer and high-quality MoS_2. Future directions and relevant important problems to be solved are also discussed.