“…In the literature, the thickness measured of a WS 2 sheet on a WS 2 substrate is equal to 0.6 nm [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Therefore, our data are consistent with what previously reported, considering the error bar.…”