Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
School of Materials Science and Engineering, Nanchang University, Nanchang, Jiangxi 330031, China.
Nat Commun. 2016 Jul 14;7:12206. doi: 10.1038/ncomms12206.
A microscopic understanding of the growth mechanism of two-dimensional materials is of particular importance for controllable synthesis of functional nanostructures. Because of the lack of direct and insightful observations, how to control the orientation and the size of two-dimensional material grains is still under debate. Here we discern distinct formation stages for MoS2 flakes from the thermolysis of ammonium thiomolybdates using in situ transmission electron microscopy. In the initial stage (400 °C), vertically aligned MoS2 structures grow in a layer-by-layer mode. With the increasing temperature of up to 780 °C, the orientation of MoS2 structures becomes horizontal. When the growth temperature reaches 850 °C, the crystalline size of MoS2 increases by merging adjacent flakes. Our study shows direct observations of MoS2 growth as the temperature evolves, and sheds light on the controllable orientation and grain size of two-dimensional materials.
对二维材料生长机制的微观理解对于可控合成功能纳米结构尤为重要。由于缺乏直接而有见地的观察，如何控制二维材料晶粒的取向和大小仍存在争议。在这里，我们使用原位透射电子显微镜从硫钼酸铵的热解中分辨出 MoS2 薄片的不同形成阶段。在初始阶段（400°C），MoS2 结构以逐层模式垂直生长。随着温度升高至 780°C，MoS2 结构的取向变为水平。当生长温度达到 850°C 时，通过合并相邻的薄片，MoS2 的晶体尺寸增大。我们的研究表明了随着温度的演变，MoS2 生长的直接观察，并为二维材料的可控取向和晶粒尺寸提供了启示。
