Layer number dependence of the work function and optical properties of single and few layers MoS2: effect of substrate.

We have examined the influence of flake-substrate effects that affect one and few layers of MoS2 in terms of their electrical and optical properties. In the measurements, we used SiO2/Si substrates with etched cavities and aluminum electrodes. Suspended areas are easily identifiable both on images depicting the topography and on the surface potential maps measured with the Kelvin probe force microscopy. Compared to the SiO2/Si supported material, surface potential decrease is observable at the membrane. The surface potential value of the flakes located on the electrodes is the lowest. PL measurements prove that single MoS2 monolayer was obtained. Suspended regions are also correlated with maps obtained as a result of Raman spectroscopy.