Growth of Large-Area and Highly Crystalline MoS₂ Thin Layers on Insulating Substrates

TLDR

Molybdenum disulfide is prized for its direct‑gap properties and potential in optoelectronics and energy harvesting, yet scalable, high‑quality large‑area synthesis remains uncommon. The study aims to demonstrate that high‑temperature annealing of ammonium thiomolybdate in sulfur yields large‑area MoS₂ layers with superior electrical performance on insulating substrates. The method involves thermally decomposing ammonium thiomolybdate and annealing it in sulfur at high temperature to form MoS₂ on insulating substrates. The resulting MoS₂ sheets are highly crystalline, exhibit electron mobilities comparable to exfoliated flakes, and the process is simple, scalable, and transferable to arbitrary substrates, enabling layered composites.

Abstract

The two-dimensional layer of molybdenum disulfide (MoS2) 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 MoS2 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 MoS2 thin layers with superior electrical performance on insulating substrates. Spectroscopic and microscopic results reveal that the synthesized MoS2 sheets are highly crystalline. The electron mobility of the bottom-gate transistor devices made of the synthesized MoS2 layer is comparable with those of the micromechanically exfoliated thin sheets from MoS2 crystals. This synthetic approach is simple, scalable and applicable to other transition metal dichalcogenides. Meanwhile, the obtained MoS2 films are transferable to arbitrary substrates, providing great opportunities to make layered composites by stacking various atomically thin layers.