Figure 2.

(a) The optical image of a representative etched sample consisting of flakes with the different number of layers including 1, 2, 3, 8, 19, 22, and 71 layers. SM denotes the MoS₂ residues due to imcomplete removal of monolayer. (b) AFM image of the area squared in (a). (c) AFM depth profiles showing 1, 2 and 3 layers of MoS₂ as marked by blue lines in (b). (d) The optical image of the same sample after another 7 min fine etching showing that 7 MoS₂ layers have been removed uniformly from all domains starting with more than 7 layers.