Fig. 6
(a) Optical microscope image of the location of the flakes with minimal contrast of SiO2 layer on Si wafer, (b) SFM-TM height image of the pyramidal layered flakes assigned to WS2. (c) Height profile line as shown in (b), each step is 0.6 nm. (d) SFM-QI Pull off or Adhesion force image at the edge area of the flakes with low optical contrast. (e) SFM-QI height image of the edge of the flake seen as low contrast in the (a). (f) Height Distribution of the rectangular area seen in (e), showing the height of the low optical contrast area to be 1.35 nm, which is assigned to a bi-layer structure of the WS2 at the SiO2 layer of the Si wafer.
