posted on 2020-05-08, 18:07authored byGang Peng, Xi Yang, Siyuan Wang, Jianyu Zhang, Gongjin Qi, Sen Zhang, Ken Liu, Zhi Hong Zhu, Zheng Li, Guang Wang, Mengjian Zhu, Shiqiao Qin
The
stacking order plays a critical role in the electronic and optical
properties of two-dimensional materials. It is however of great challenge
to achieve large-size and homogeneous bilayer crystals with precisely
controlled stacking orders. Here, we demonstrate an optimized chemical
vapor deposition strategy to grow MoSe2 bilayers with controlled
AA or AB stacking sequences. Reverse gas flow effectively suppresses
the random nucleation centers, leading to uniform growth of the second
layer of MoSe2 on the first monolayer. A customized temperature
profile selectively activates the growth of the MoSe2 bilayer
with different stacking orders: the AA stacking MoSe2 bilayer
tends to form at 810 °C, and the AB stacking MoSe2 bilayer prefers to grow at a higher temperature of 860 °C.
A series of characterization methods confirm that MoSe2 bilayers with different stacking orders exhibit distinct crystal
structures and physical properties. Our results demonstrate a robust
and effective route for the controllable synthesis of transition metal
dichalcogenide bilayers, which will benefit the development of two-dimensional
materials and van der Waals heterostructures.