Size and shape control of CVD-grown monolayer MoS2

Molybdenum disulfide (MoS2) has attracted great attention because of its unique physical properties and wide potential applications in electronic, optoelectronic devices. Chemical vapor deposition (CVD) turned out to be a powerful tool for producing MoS2 thin layers. Nonetheless, how the concentration of vapor-phase precursor influences the size and shape change of MoS2 is not clearly understood yet. In this work, we designed a gradient of sulfur (S) concentration during CVD growth of MoS2 to investigate how S concentration affects its size and shape change. The shape of MoS2 film changes from triangle to hexagon, then back to triangle as S concentration decreases. We also analyzed the uniformity and crystal quality of the CVD-grown MoS2 by using optical mi-croscopy, Raman, photoluminescence (PL), circularly polarized PL, and atomic force microscopy.