Large-Domain Growth of MoS2 by Heterogeneous Oxygen-Assisted MOCVD

After the discovery of graphene, two-dimensional materials (2DMs) have gained significant attention in that they exhibit unique properties different from conventional bulk materials. Among them, MoS₂ is expected to become a promising next-generation semiconductor material due to its band gap. The most commonly used method for synthesizing MoS2 is metal-organic chemical vapor deposition (MOCVD) using gaseous metal-organic molecules in transition metal precursors. A number of previous studies have reported homogeneous nucleation in MOCVD, where the gaseous Mo and S precursors react in air before they are deposited on a substrate. However, homogeneous nucleation in MOCVD raises issues such as difficulty in growing large domains with longer processing time.
Here, we show that oxygen-assisted heterogeneous nucleation expands the domain size up to 100 μm in 20 min. Unlike homogeneous nucleation, the heterogeneous nucleation is found to promote the growth of larger particles by separating MO precursor deposition and sulfurization steps. We also find that oxygen gas in the deposition stage accelerates the reaction and NaCl(s) suppresses the nucleation density, which is critical for scale-up, resulting in ~2,000 times larger grain sizes. Thus, we expect that our results would contribute to the commercial application of TMDCs, which has been limited by small domain sizes and the prolonged synthesis time.