The resulting local spectra can be summed over regions of interest (RoI's) with freely defined shapes as applied on measurements discussed in the following. In particular, microscopic measurements of the work function contrast have proven to be a very sensitive method for distinguishing monolayer and few-layer regions of TMDC flakes. First, we will discuss the work function contrast of selected MoS2 flakes prepared on naturally oxidized silicon and titanium substrates. In the following, we will refer to the flake on the oxidized silicon substrate (Figure , d and Fig. , Fig. ) as flake 1, while the two flakes on the titanium substrates are referred to as flake 2 (Figure , e and Fig. , Fig. ) and flake 3 (Figure , f and Fig. , Fig. ). Figure shows PEEM images (the total diameter of the field of view is 126 μm for the measured circular images, the figures shown are cutouts and the scales are adjusted accordingly) together with the normalized μ-PES spectra of the secondary electron cutoff. Regions of interest (denoted R1 -R4 in Figure ) were selected based on previously acquired optical microscope images and observable color variations (Figure ). Average spectra in Figure -f were generated over all pixels in the chosen regions marked in Figures . For a better comparison of the work functions, we measured the secondary electron cutoff from the pure substates with ultraviolet photoelectron spectroscopy (UPS) at our laboratory spectrometer. We found a work function of 4.2 eV and 3.6 eV for the silicon and titanium substrates, respectively (Figure ). This difference is in good agreement with literature data and the relative differences we found in our PEEM measurements on the substrate. Therefore, we referenced the work functions of the substrates to those value and adjusted the values for the MoS2 flake regions based on the relative differences.