Atomistic Kinetics of Dislocation‐Mediated Grain Growth in Monolayer MoS 2

ABSTRACT Grain boundaries (GBs) in 2D materials are arrays of dislocations that strongly influence electronic, optical, mechanical, and transport properties. In monolayer MoS 2 , Mo 5|7 and S 5|7 dislocation cores are structurally established, yet how their distinct mobilities govern GB migration and grain growth has remained unresolved. Here, we directly image and quantify GB mobility in polycrystalline monolayer MoS 2 at the level of individual dislocation cores. An atomic‐scale in‐situ heating study reveals that mobile GBs consist solely of Mo 5|7 dislocations, whereas immobile GBs contain S 5|7 kink sites that suppress GB motion. Dark‐field TEM grain‐growth measurements show that mobile GBs drive rapid coarsening, while S 5|7‐pinned immobile GBs arrest microstructural evolution. Molecular dynamics simulations correlate this mobility contrast with distinct local mechanical and energet…