Inherent Resistance of Seed-Mediated Grown MoSe₂ Monolayers to Defect Formation

Recent progress in the chemical vapor deposition technique toward growing large-area and single-crystalline two-dimensional (2D) transition metal dichalcogenides (TMDs) has resulted in an electronic/optoelectronic device performance that rivals that of their top-down counterparts, despite the extensive use of hydrogen, a common reducing agent that readily generates defects in TMDs. Herein, we report that 2D MoSe2 domains containing oxide seeds are resistant to hydrogen-induced defect generation. Specifically, we observed that the etching of the edges of seed-containing MoSe2 was significantly less than that of pristine MoSe2, without apparent seed particles, under the same H2 annealing conditions. Our systematic approach for controlling the H2 exposure time indicates that the oxidation of Mo and the edge roughening of seedless MoSe2 coincidentally increase after H2 exposure owing to the formation of Se vacancy followed by Mo oxidation, which is not the case with seed-containing MoSe2. An ab initio calculation indicates that hydrogen preferentially adsorbs more onto O bonded to Mo than onto Se, providing further evidence of the resistance of seeded MoSe2 to hydrogen etching. This finding provides an insight into controlling defect formation in 2D TMDs by employing sacrificial adsorption sites for reactive species (i.e., hydrogen).