Atomic scale study for the structural evolution of monolayer 1T′-MoS₂

Two-dimensional transition metal dichalcogenides (2D-TMDs) exhibit diverse polymorphic configurations characterized by distinct atomic arrangements and electronic properties. Harnessing phase transitions in TMDs can overcome spatial and technical limitations of conventional semiconductor fabrication, driving advancements in next-generation optoelectronics and energy conversion technologies. Herein, by performing in situ atomic-resolution characterization employing aberration-corrected scanning transmission electron microscopy (AC-STEM), the dynamic structural evolution in monolayer 1T′-MoS₂ were directly observed. Our observations demonstrate that the dynamic recombination of molybdenum-molybdenum bonds within the characteristic zigzag chains facilitates the formation of tetrameric metal clusters and subsequently induces a newly oriented zigzag chains of molybdenum, ultimately establishing anisotropic configurations. Notably, the 2H/1T′ grain boundaries maintain atomically sharp and coherent interfaces devoid of detectable lattice strain-a critical feature for constructing high-performance heterostructure devices requiring precise interfacial charge transport. These atomic-scale insights into structural evolution mechanisms not only advance fundamental understanding of phase transformation dynamics in 2D materials, but also provide crucial design principles for engineering metastable-phase architectures in functional nanoelectronics.