In Situ Atomic-Scale Visualization of Interface Relaxation Pathways and Stacking-Registry Evolution in 2D MoS2

Understanding transient kinetic pathways governing the bottom-up synthesis of 2D MoS2 is critical for deterministic growth. Here, utilizing an atomically resolved graphene-based microreactor for in situ heating transmission electron microscopy, we directly visualize the interface relaxation pathways and stacking-registry evolution during the growth of MoS2, advancing beyond the mere observation of its continuous growth dynamics. We reveal that lateral expansion is driven by dynamic edge reconstructions, as kinetically metastable states spontaneously relax into thermodynamically favored zigzag configurations. During subsequent domain coalescence, the dynamic interface relaxation is achieved across three distinct modes: defect-forming gap healing, strain-regulated seamless stitching, and rigid-body oriented attachment, which robustly accommodate lattice misorientations. Furthermore, intrinsic in-plane mirror twin boundaries induce localized structural distortions that mediate out-of-plane interlayer sliding, transiently stabilizing nonequilibrium bilayer stacking registries. By resolving these dynamic atomic fluctuations, our work establishes a fundamental mechanistic framework linking growth kinetics to the synthesis of 2D materials.