Toward a Mechanistic Understanding of Vertical Growth of van der Waals Stacked 2D Materials: A Multiscale Model and Experiments

Abstract

Vertical stacking of monolayers via van der Waals (vdW) interaction opens promising routes toward engineering physical properties of two-dimensional (2D) materials and designing atomically thin devices. However, due to the lack of mechanistic understanding, challenges remain in the controlled fabrication of these structures via scalable methods such as chemical vapor deposition (CVD) onto substrates. In this paper, we develop a general multiscale model to describe the size evolution of 2D layers and predict the necessary growth conditions for vertical (initial + subsequent layers) versus in-plane lateral (monolayer) growth. An analytic thermodynamic criterion is established for subsequent layer growth that depends on the sizes of both layers, the vdW interaction energies, and the edge energy of 2D layers. Considering the time-dependent growth process, we find that temperature and adatom flux from vapor are the primary criteria affecting the self-assembled growth. The proposed model clearly demonstrates the distinct roles of thermodynamic and kinetic mechanisms governing the final structure. Our model agrees with experimental observations of various monolayer and bilayer transition metal dichalcogenides grown by CVD and provides a predictive framework to guide the fabrication of vertically stacked 2D materials.

Controlled Vapor Growth and Nonlinear Optical Applications of Large‐Area 3R Phase WS2 and WSe2 Atomic Layers

“…Generally, low flow rate and high evaporation temperature lead to the decreasing of adatoms and nucleation sites on the substrate, which makes the growth of multilayer more favorable. Meanwhile, long growth time helps the growth of top layers, thus leading to a high or full covered structure . In this way, we can control almost 90% of the layers with fully covered top layer in the desired region, instead of the terrace‐growth mechanism with gradually layer‐by‐layer shrinking at the center.…”

Temperature Difference Triggering Controlled Growth of All‐Inorganic Perovskite Nanowire Arrays in Air

“…However, precursor and deposition substrate is so closely contacted that they are likely to share the same temperature. As we know, growth of material is the result of competition between composing and decomposing processes under certain temperature . Growth occurs when composing prevails but etching takes place once decomposing dominates the game .…”

Controlled Growth of Large-Area Bilayer Tungsten Diselenides with Lateral P–N Junctions

“…20,40,42 The addition of NaCl transforms some WOx into oxyhalide (WOxCl), which is more easily evaporated at high temperature, leading to increased W adatom flux from the vapor and enhanced growth of the bilayer (Figure 1b). 20,43,44 When pure NaCl is used as the growth promoter, a large amount of WOxCl forms, leading to reduced surface adsorption and further increased W vapor adatom flux, so that multilayer (ML) WSe2 dominates the final structures (Figure 1c). Figure 2 shows optical micrographs of WSe2 flakes grown using these three different promoter mixtures.…”