Figure 5.

(a) Schematic band diagrams to explain the relation used in KPFM measurements, WF = WF_tip − eV_S, where WF, WF_tip, e, and V_S are the work function of a sample (MoS₂), the work function of the tip, the electron charge, and the surface potential, respectively. E_vac, E_C, E_F, and E_V are the vacuum level, conduction band minimum, Fermi level, and the valence band minimum of a sample, respectively. (b) The interfacial electric dipole energy, Δϕ, lowers the WF of the MoS₂ region on the Au stripe (WF-S). It should be noted that eV_S = WF_tip − WF. The band diagrams in (a,b) indicate V_S < 0, consistent with our experimental results. Thus, reduction of WF increases V_S and decreases |V_S| (V_S < 0), as illustrated in (b). Schematic band diagrams and illustration of the MoS₂ monolayers on the Au stripe arrays in the dark, when including (c) only strain-induced bandgap reduction and (d) additional electronic interaction at the MoS₂/Au interface.