Role of nuclei in controllable MoS2 growth by modified chemical vapor deposition
The large area and high-quality two-dimensional molybdenum disulfide (2D-MoS2) film has been synthesized by a modified single-zone chemical vapor deposition technique. The influence of gas environment, reaction temperature and gap distance (between MoO3 precursor and substrate) on 2D-MoS2 growth were systematically investigated. A stable gas environment was prerequisite for the formation of 2D-MoS2, and it can be achieved by adjusting the pressure and flow rate of N2 in the furnace tube, which was numerical estimated via Antoine equation. The thickness, quality (uniformity and crystallinity), roughness, and chemical composition of the MoS2 nano-film were characterized by the optical microscopy, scanning electron microscope, Raman spectroscopy, Atomic force microscope, and X-ray photoelectron spectroscopy, respectively. The results showed that the quality of MoS2 nano-film was greatly influenced by the nucleation density on the substrate, which could be controlled by modulating the reaction temperature and gap distance. Moreover, a “frustum-like” model was established to match the practical reaction situation and clarify the internal relationship among reaction temperature, gap distance and the nucleation density of MoS2 film. Finally, a high-quality monolayer MoS2 nano-film, at 800 °C with a gap distance of 3.5 mm, was obtained and verified by experimental and numerical analyses.
This work was partly supported by the National Natural Science Foundation of China (Nos. 61674099, 61274067 and 60876045), and the R&D Foundation of SHU-SOENs PV Joint Lab (No. SS-E0700601). One of the authors (Wenlei Song) appreciate Dr. Jianwei Shi of Arizona State University for his helpful revision and discussion of the manuscript.
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