Fig. 1: Morphological evolution of monolayer MoS₂ from triangular to ribbon-like shaped domains.

a Schematic illustration of the morphological evolution of MoS₂. b, c SEM images of 2D monolayer MoS₂ triangles (b) and 1D ribbons (c) achieved at different S/Mo ratios. d Nucleation barrier (ΔE) difference mapping between S-zz and Mo’-zz edges under different chemical potentials of Mo (μ_Mo) and S (μ_S). For the case of high μ_S and low μ_Mo (bottom right region), the nucleation barrier of S-zz is smaller than that of Mo’-zz edge (ΔE < 0), Mo’-zz edge is the dominating edge and the resulted MoS₂ flake presents a triangle shape. As μ_S decreases (ΔE > 0, bottom left region), the S-zz edge becomes the dominating edge and the resulted MoS₂ flake shows quasi ribbon-like shape. e Schematic view showing the morphology variations of monolayer MoS₂ islands with decreasing the S/Mo ratio. Orange and yellow spheres indicate Mo and S atoms, while the orange and yellow lines represent Mo and S terminated edges, respectively.