Identification and characterization of freely suspended MoS
nanosheets. (a) Color chart displaying the calculated color for MoS2 nanosheets with different number of layers laying on the substrate (supported) or covering a hole (suspended). (b) Optical micrograph of a 4.8-nm-thick (8 layers) MoS2 flake deposited on top of a 285-nm SiO2/Si substrate pre-patterned with an array of holes 1.1 μm in diameter. Even though the flake covers two holes, it is thin (and transparent) enough to permit optical identification of the covered holes, which present a slightly different color from the uncovered holes, as predicted by the color chart shown in (a). (c) Contact mode AFM topography of the region marked by the rectangle in (b); (inset) topographic line profile acquired along the dashed line in (c). (d) and (e) Raw friction forward images acquired in contact mode AFM in a suspended and a supported region, marked by a red circle and a blue square in (c), respectively. The insets in (d) and (e) show two friction images simulated with a two-dimensional Tomlinson model. Both images have been simulated employing the same crystal lattice and orientation but different depth of the potential well (see text for a full discussion).