Effect of Mo concentration on shape and size of monolayer MoS2 crystals by chemical vapor deposition

Abstract

Monolayer molybdenum disulfide (MoS2), a new two-dimensional direct-bandgap semiconductor, has attracted research interests into applications in atomically thin electronics and optoelectronics. Growing monolayer MoS2 film by chemical vapor deposition is the most commonly used approach. Little is known, however, about the cause of the shape and size evolution. Here, we explore how the precursor’s concentration affects the MoS2 crystals’ shape and size. When S concentration is stable, the shape of the MoS2 domain evolves from triangle to hexagon and then truncated triangle, finally back to a triangle as the concentration of Mo elevates. Regulating the concentration of Mo leads to the controllable growth of MoS2 crystal. By controlling the concentration of Mo, we eventually synthesized over 100 µm monolayer MoS2 crystals. Our results are a significant step forward in realizing the ultimate promise of large atomic MoS2 monolayer crystals for flexible, electronic, optoelectronic devices.