Growth of large-area and highly crystalline MoS ₂ thin layers on insulating substrates

The two-dimensional layer of molybdenum disulfide (MoS ₂) has recently attracted much interest due to its direct-gap property and potential applications in optoelectronics and energy harvesting. However, the synthetic approach to obtain high-quality and large-area MoS ₂ atomic thin layers is still rare. Here we report that the high-temperature annealing of a thermally decomposed ammonium thiomolybdate layer in the presence of sulfur can produce large-area MoS ₂ thin layers with superior electrical performance on insulating substrates. Spectroscopic and microscopic results reveal that the synthesized MoS ₂ sheets are highly crystalline. The electron mobility of the bottom-gate transistor devices made of the synthesized MoS ₂ layer is comparable with those of the micromechanically exfoliated thin sheets from MoS ₂ crystals. This synthetic approach is simple, scalable, and applicable to other transition metal dichalcogenides. Meanwhile, the obtained MoS ₂ films are transferable to arbitrary substrates, providing great opportunities to make layered composites by stacking various atomically thin layers.