Thermodynamically Driven Tilt Grain Boundaries of Monolayer Crystals Using Catalytic Liquid Alloys

We report a methodto precisely control the atomic defectsat grainboundaries (GBs) of monolayer MoS2 by vapor-liquid-solid(VLS) growth using sodium molybdate liquid alloys, which serve asgrowth catalysts to guide the formations of the thermodynamicallymost stable GB structure. The Mo-rich chemical environment of thealloys results in Mo-polar 5|7 defects with a yield exceeding 95%.The photoluminescence (PL) intensity of VLS-grown polycrystallineMoS(2) films markedly exceeds that of the films, exhibitingabundant S 5|7 defects, which are kinetically driven by vapor-solid-solidgrowths. Density functional theory calculations indicate that theenhanced PL intensity is due to the suppression of nonradiative recombinationof charged excitons with donor-type defects of adsorbed Na elementson S 5|7 defects. Catalytic liquid alloys can aid in determining atype of atomic defect even in various polycrystalline 2D films, whichaccordingly provides a technical clue to engineer their properties.