Multiscale Simulation Method Development and Application in Two-Dimensional Functional Materials

The unique properties of two-dimensional (2D) materials make them the potential solutions to a wide variety of engineering challenges, especially in electronic device engineering. In order to realize their application potentials, three tasks must be fulfilled, namely the thorough understanding of the material properties, the suitable application design, and synthesis route development for the mass production of the materials. Currently, the first two tasks are in relatively mature stages; however, the bottom-up synthesis method development of 2D materials, especially 2D compound materials, is still at an early stage, due to a limited theoretical understanding of the mechanisms of the submonolayer growth of the 2D crystalline compounds. In this dissertation, the author presents the development and application of multiple simulation tools, including density functional theory, kinetic Monte Carlo method, and phase field method to study the growth mechanism of 2D compounds. Transition metal dichalcogenides (TMDs) are taken as a representative example. The multiscale simulation methods can be used to analyze the nucleation and growth processes during the deposition of TMDs. The formation and influence of material imperfections, such as point defects, metal clustering, screw dislocations, etc., are also studied with these simulation tools. With the help of the established simulation toolbox, the author contributes to the understanding of the physics behind this complex catalog of atomic processes involved in the synthesis of TMDs. The simulation tools and the results thereof provide guidance to the experimental efforts, and have supported the joint efforts towards the realization of large-scale production of electronic-grade 2D semiconductors. In addition, the author also presents his theoretic works on the investigation of electric properties of 2D functional materials and their contact/combination systems, the novel device design based on these understandings, and the method pathfinding in neural-networks based interatomic potentials. The studies presented in this dissertation, from one facet, exhibit the wide application potential of multiscale simulation tools on materials science research and engineering.