Abstract
Controlled anisotropic growth of two-dimensional materials provides an approach for the synthesis of large single crystals and nanoribbons, which are promising for applications as low-dimensional semiconductors and in next-generation optoelectronic devices. In particular, the anisotropic growth of transition metal dichalcogenides induced by the substrate is of great interest due to its operability. To date, however, their substrate-induced anisotropic growth is typically driven by the optimization of experimental parameters without uncovering the fundamental mechanism. Here, the anisotropic growth of monolayer tungsten disulfide on an ST-X quartz substrate is achieved by chemical vapor deposition, and the mechanism of substrate-induced anisotropic growth is examined by kinetic Monte Carlo simulations. Results show that, besides the variation of substrate adsorption, the chalcogen to metal (C/M) ratio is a major contributor to the large growth anisotropy and the polarization of undergrowth and overgrowth; either perfect isotropy or high anisotropy can be expected when the C/M ratio equals 2.0 by properly controlling the linear relationship between gas flux and temperature.
Highlights
Transition metal dichalcogenides (TMDCs) have been a star family of two-dimensional (2D) materials,[1] which is attributed to their excellent electronic and optical properties
To enable the direct growth of large single crystals and nanoribbons by chemical vapor deposition (CVD),[10] the flake alignment of 2D materials can be one of key factors and the growth anisotropy should be intensively investigated, since it has been shown that the waferscale single-crystalline graphene can be grown if the initial graphene nuclei have the same orientation[11] and the alignment of monolayer TMDC nanoribbons is largely determined by the orientation of the crystal substrate.[12,13]
It has been found that the morphology of TMDC flakes varies from upward triangle to downward triangle and to hexagon due to the variation of conditions such as temperature (T), gas flux (Ra, defined as the adsorption rate of W atoms in the kinetic Monte Carlo (kMC) model), the chalcogen to metal (C/M) ratio, and substrate adsorption contrast
Summary
Transition metal dichalcogenides (TMDCs) have been a star family of two-dimensional (2D) materials,[1] which is attributed to their excellent electronic and optical properties. Systematic understanding of the anisotropic growth of monolayer TMDCs is a theoritical challenge due to the diversity of involved kinetic mechanisms and the wide range of growth conditions (e.g., gas flux, C/M ratio, temperature, and substrate conditions).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
