title: Direct TEM observations of growth mechanisms of two-dimensional MoS2 flakes.
abstract: 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.
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: Linfeng
authors.initials: L
authors.lastname: Fei
authors.affiliation: School of Materials Science and Engineering, Nanchang University, Nanchang, Jiangxi 330031, China.
authors.forename: Shuijin
authors.initials: S
authors.lastname: Lei
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.|School of Physics and Electronic Sciences, Changsha University of Science and Technology, Changsha 410004, China.
authors.forename: Wei-Bing
authors.initials: WB
authors.lastname: Zhang
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: Ziyuan
authors.initials: Z
authors.lastname: Lin
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: Chi Hang
authors.initials: CH
authors.lastname: Lam
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Chai
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China.|School of Materials Science and Engineering, Nanchang University, Nanchang, Jiangxi 330031, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang