Fig. 1. (a) Schematic diagram of the CVD setup for growth of MoS₂. The locations of S, MoO₃, and SiO₂/Si substrate are exactly displayed. (b) Schematic of the growth of MoS₂ with the extra H₂O sources. (c) Schematic of the conventional triangular growth of MoS₂ without H₂O sources.

Fig. 2. (a), (e) Microscopic optical photographs, (b), (f) fluorescence spectra, (c), (g) phase diagrams of AFM images, and (d), (h) photoluminescence (PL) spectra for (a)–(c) dendrite and (e)–(g) conventional triangular monolayers MoS₂, respectively. Scale bar: (a), (b) = 50 µm, (e), (f) = 10 µm, (c), (g) = 6 µm.

Fig. 3. (a) Bright-field image of a uniform MoS₂ dendrite with a large size. (b) Diffraction pattern of the area marked with black circle in (a) and the vector indicate the two families, K_S and K_Mo. (c) Amplitude of the AFM image of the prepared monolayer MoS₂ by water-assisted CVD procedure. (d) A line scan profile shows the diffraction intensity of framed spots in (b). (e) Representative Raman spectrum of the monolayer MoS₂ dendrites grown on Si/SiO₂ substrate. (f) shows the line profile along the white line in (c). The measured thickness of the monolayer is ∼1 nm.

Fig. 4. (a) Schematic diagram of growth of MoS₂ in the representative regions of I, II, III. (b)–(d) Optical microscopy (OM) images of the monolayer MoS₂ in the regions of I, II, III, respectively. The domain evolves from the isolated monolayer in I to the continuous MoS₂ flakes in III. (e)–(g) are the fluorescence spectroscopy (FM) images corresponding to (b)–(d), respectively. The intensity of fluorescence increases gradually from (e) to (g). (h) PL intensity in areas I, II, and III of the monolayer MoS₂, respectively. Scale bars: 100 µm.

Fig. 5. Analysis of the CVD-grown uniform dendritic monolayer MoS₂ morphology. (a) Fluorescence microscope image for uniform dendritic monolayer MoS₂. The hierarchical structures are marked by arrows, i.e., yellow for primary backbone, green and blue for the secondary and tertiary branches. The axial angles between different hierarchical branches (I and II, II, and III) have the same 120° angle. (b) The close-ups of areas marked by the solid rectangles in (a). (c) Atomic structure arrangement diagram of uniform dendritic MoS₂. The region in the red circle has more defects, where fluorescence is stronger.