Figure 4: Validity of the SE contrast model and work function extraction.
(a) SE energy spectrum for freestanding monolayer graphene. The result contains raw data (black open circles), smoothed spectrum (red line) and spectrum fitted by Chung and Everhart model (blue dashed line). The spectrum exhibits a maximum peak around a SE energy of 1.5 eV and can be well fitted by Equation (3) with
. The fitting value of work function for the freestanding monolayer graphene is 4.33 eV. (b) SE spectrum of the substrate supported monolayer graphene (red line), in comparison with the spectra of freestanding monolayer graphene (blue line) and the substrate (black line). The green dashed line shows the spectrum calculated by our SE contrast model. (c) Band structure diagram of graphene on a SiO2/Si substrate. The band structures of the Si substrate, SiOayer, monolayer and quad-layer graphene are shown in the diagram from left to right.
