Monolayer MoS₂ Growth on Au Foils and On‐Site Domain Boundary Imaging

Controllable synthesis of large domain, high‐quality monolayer MoS₂ is the basic premise both for exploring some fundamental physical issues, and for engineering its applications in nanoelectronics, optoelectronics, etc. Herein, by introducing H₂ as carrier gas, the successful synthesis of large domain monolayer MoS₂ triangular flakes on Au foils, with the edge length approaching to 80 mm is reported. The growth process is proposed to be mediated by two competitive effects with H₂ acting as both a reduction promoter for efficient sulfurization of MoO₃ and an etching reagent of resulting MoS₂ flakes. By using low‐energy electron microscopy/diffraction, the crystal orientations and domain boundaries of MoS₂ flakes directly on Au foils for the first time are further identified. These on‐site and transfer‐free characterizations should shed light on the initial growth and the aggregation of MoS₂ on arbitrary substrates, further guiding the growth toward large domain flakes or monolayer films.