Mechanism of substrate-induced anisotropic growth of monolayer WS2 by kinetic Monte Carlo simulations

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. These 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.Keywords: anisotropic growth, monolayer tungsten disulfide, kinetic Monte Carlo, ST-X quartz substrate, chemical vapor depositionRecently, substrates such as sapphire, mica, graphite [18][19][20][21] have been used in the alignment of as-grown TMDC flakes, which is attributed to the

Space-confined and substrate-directed synthesis of transition-metal dichalcogenide nanostructures with tunable dimensionality

“…Under such local spaceconfined environment, we propose that the kinetic growth can be induced combined with vdW substrate effect. Recent kinetic Monte Carlo simulation results have also predicted the substrate-induced anisotropic growth of WS 2 NRs, which further confirms our experimental results [36]. Our methods pave a new route for the control-lable growth of TMDC NRs, which is significant for exploring promising applications based on TMDC NRs.…”

Epitaxial Growth of Rectangle Shape MoS2 with Highly Aligned Orientation on Twofold Symmetry a‐Plane Sapphire

“…The comparisons suggest that the anisotropic growth of MoS 2 is most possibly induced by the anisotropic property of substrate: including surface adsorption and surface diffusion, which are considered as two key factors that influence the topological evolution of TMDs and would result in the anisotropy growth. [ 44 ] Actually, the twofold symmetry surface structure of a‐plane sapphire makes it an intrinsic anisotropic substrate. In this regard, the anisotropic substrate induces symmetry breaking of incipient MoS 2 seed and enables rapid crystal growth in one direction owing to the highly asymmetric energy landscape experienced by the MoS 2 crystal.…”

Ultrafast growth of large single crystals of monolayer WS2 and WSe2

“…At higher temperatures, the migration coefficient is larger and adatoms can diffuse over longer distances before attaching to an island. Recent theoretical calculations showed that the migration energies of W and S atoms on the edge site of WS 2 are about 3.81 eV and 1.02 eV, respectively [ 53 ]. Thus, the lateral growth of WS 2 is mainly limited by W migration with a migration barrier of 3.81 eV.…”