Abstract
Controlled growth of crystalline solids is critical for device applications, and atomistic modeling methods have been developed for bulk crystalline solids. Kinetic Monte Carlo (KMC) simulation method provides detailed atomic scale processes during a solid growth over realistic time scales, but its application to the growth modeling of van der Waals (vdW) heterostructures has not yet been developed. Specifically, the growth of single-layered transition metal dichalcogenides (TMDs) is currently facing tremendous challenges, and a detailed understanding based on KMC simulations would provide critical guidance to enable controlled growth of vdW heterostructures. In this work, a KMC simulation method is developed for the growth modeling on the vdW epitaxy of TMDs. The KMC method has introduced full material parameters for TMDs in bottom-up synthesis: metal and chalcogen adsorption/desorption/diffusion on substrate and grown TMD surface, TMD stacking sequence, chalcogen/metal ratio, flake edge diffusion and vacancy diffusion. The KMC processes result in multiple kinetic behaviors associated with various growth behaviors observed in experiments. Different phenomena observed during vdW epitaxy process are analysed in terms of complex competitions among multiple kinetic processes. The KMC method is used in the investigation and prediction of growth mechanisms, which provide qualitative suggestions to guide experimental study.
Highlights
Since the isolation of graphene and the re-introduction of layered two-dimensional (2D) materials[1,2,3] and the subsequent revival of single or few layer transition metal dichalcogenides (TMDs)[4], this family of 2D TMD materials has attracted great research interest
The density functional theory (DFT) simulation is able to provide reliable predictions on the structural and electronic properties of the materials. These methods are limited to the study of unit atomic processes in modeling TMD growth processes, but are not capable of approaching a dynamic process deviating from an equilibrium and with a macroscopic time range
In order to address these challenges, two kinetic methods have been adapted to simulate the dynamic evolution of 2D materials system, namely the kinetic Monte Carlo (KMC)[28, 29] and the phase field model (PFM)[30]
Summary
Since the isolation of graphene and the re-introduction of layered two-dimensional (2D) materials[1,2,3] and the subsequent revival of single or few layer transition metal dichalcogenides (TMDs)[4], this family of 2D TMD materials has attracted great research interest. The DFT simulation is able to provide reliable predictions on the structural and electronic properties of the materials These methods are limited to the study of unit atomic processes (e.g., atomic adsorption/desorption, surface diffusion, edge diffusion) in modeling TMD growth processes, but are not capable of approaching a dynamic process deviating from an equilibrium and with a macroscopic time range. Especially a binary-tree searching engine[41], and a high level of details make it possible to accurately simulate and effectively describe the competing factors that cause many phenomena important to the TMD material growth processes and atomic scale mechanisms This model brings insight to the fine control of the vdW epitaxy of the TMDs. The current KMC model provides a quantitatively accurate model for MBE growth of TMDs, and with further refinements it could be used to make both qualitative and quantitative predictions for CVD growth processes. Event selection and execution: generating a random number ξ1 ∈ [0,1), and the q th process that makes
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