Controlled anisotropic growth of two-dimensional (2D) materials provides a distinct approach for the synthesis of large single crystals and nanoribbons, which will be very promising due to its potential applications in low-dimensional semiconductors and next-generation optoelectronic devices. In particular, the anisotropic growth of transition metal dichalcogenides (TMDs) induced by the substrate is of great interest due to its operability. For the first time, the proof-of-concept experiment presents the extremely anisotropic growth of monolayer tungsten disulfide (WS2) on the ST-X quartz substrate by chemical vapor deposition (CVD), and the mechanism of the substrate-induced anisotropic growth of monolayer WS2 is carefully examined by virtue of the kinetic Monte Carlo (kMC) method. In addition, we propose a quantitative method for classifying and measuring the morphology of 2D flakes and derive the formula of anisotropic growth ratio (AGR) with regard to the extent of the growth anisotropy. The results of kMC simulations show that, besides the variation of substrate adsorption, the chalcogen to metal (C/M) ratio is a major contribution to the surge of growth anisotropy and the polarization of undergrowth and overgrowth; either perfect isotropy or high anisotropy can be expected when the C/M ratio equals to 2 by properly controlling the linear relationship between gas flux and temperature.
Published in: "arXiv Material Science".