Synthesis mechanism of MoS2 layered crystals by chemical vapor deposition using MoO3 and sulfur powders

22^nd International Conference on Advanced Materials and Nanotechnology

September 19-21, 2018 Tokyo, Japan

Ji-Hoon Ahn, Se-Hun Kwon, Cheol Min Hyun, Jeong-Hun Choi, Seung Won Lee and Chang-Min Kim

Korea Maritime and Ocean University, Republic of Korea Pusan National University, Republic of Korea

Posters & Accepted Abstracts: Res. Rev. J Mat. Sci

DOI: 10.4172/2321-6212-C4-024

Abstract

Monolayer MoS2 layered crystals have attracted significant attention owing to their potential applicability in emerging devices and Chemical Vapor Deposition (CVD) is the best method so far to obtain monolayer MoS2 single crystals. Although many studies have been published on MoS2 monolayer crystals grown by CVD, there is a lack of understanding of its synthesis pathway. Therefore, in this study, we investigated the mechanism of the synthesis pathway when monolayer MoS2 crystals are synthesized by a conventional CVD method using MoO3 and sulfur powders. By analyzing the synthesized crystals and byproducts, we discovered that MoS2 crystals are synthesized on a substrate in 2D form by an intermediate phase of solid MoO2 produced by the reduction of MoO3 by sulfur, rather than being synthesized directly from vaporized MoO3 and sulfur. Based on our observations, we propose two possible reaction mechanisms for MoS2 synthesis by CVD using MoO3 and sulfur powders. First, MoS2 crystals could be mainly synthesized via reaction of MoO2 and sulfur vapors. MoO3 powder contained in the crucible would be reduced to MoO2 rather than sulfurized to MoS2 by sulfur vapor. Then, vaporized MoO2 could react with sulfur vapor to form MoS2 crystals on the substrate. Moreover, we found that MoS2 layered crystals can also be formed from pre-formed MoO2 crystals on the substrate. The two mechanisms could be occurring concurrently and the role of an intermediate phase of MoO2 is very important in both processes.

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