Controllable Synthesis of Large-Area MoSe2 Monolayer Films and Bilayer Crystals

Two-dimensional transition-metal dichalcogenides (TMDs) have attracted significant attention due to their unique layer-dependent electronic properties. Yet the growth of large-area TMDs with controllable layers has remained challenging. In this paper, we report the robust synthesis of large-area monolayer MoSe₂ films using confined chemical vapor deposition. The size of monolayer MoSe₂ films can reach approximately 1 cm. We systematically investigated the influence of growth temperature, gas flow, the Se/Mo ratio, and sodium chloride on the synthesis process. Additionally, we propose a method for growing bilayer AA and AB-stacked MoSe₂. Bilayer MoSe₂ nanoribbon, twisted bilayer MoSe₂, and substrate-mediated aligned bilayer MoSe₂ are also produced. Distinct optical properties observed in the Raman and photoluminescence spectra of bilayer MoSe₂ indicate different interlayer interactions. Our study enhances the understanding of the synthesis mechanisms behind monolayer and bilayer TMD materials and provides insights into controlling interlayer interaction in few-layer TMDs.