硫族元素取代法制备原子层厚的MoS2-MoSe2平面异质结

Synthesis of Atomically Thin MoS2-MoSe2 Planar Heterostructure By Chalcogen Substitution

本研究采用两步化学气相沉积法首先制备单层MoSe2材料,然后对其进行硫化,结合原子分辨环形暗场扫描透射电子显微镜(ADF-STEM)定量表征了不同硫化时间下样品中替代硫原子的分布。研究表明:硫原子取代优先发生在MoSe2晶畴边缘,形成MoS2-MoSe2异质结构,该异质界面进一步作为取代反应中心逐渐向MoSe2晶畴内部扩展,最终形成具有原子级平整界面的MoS2-MoSe2平面异质结。

In this work,we proposed and practiced a two-step CVD method:the MoSe2 monolayer flakes were prepared by CVD,and then such MoSe2 monolayers were sulfurized in sulfur vapor.Using atomic resolution annular dark field scanning transmission electron microscopy(ADF-STEM),we quantitatively characterized the distribution of sulfur substitution atoms within the MoSe2 crystalline lattice treated in sulfur vapor for different time.We found that the substitution of S atoms preferentially occurs in the domain edges,forming MoS2-MoSe2 heterostructure.The interface of heterostructure acts as a substitution reaction center,driving the interface gradually moving into the inner domain of MoSe2.Finally,a monolayer MoS2-MoSe2 planar heterostructure is formed.The planar heterostructure prepared by our two-step CVD method shows atomically sharp interface.Our results are important in the controllable growth of high quality TMD alloys and heterojunctions.