(color online) (a) Optical image of lateral WS₂/WSe₂ heterojunction.^[97] (b) I_ds–V_ds characteristics in the dark and under laser illumination (514 nm, 30 nW). The inset shows the photocurrent response under periodic on/off laser illumination.^[97] (c) Color-coded rendering of the real space imaging of band profile plotted in terms of log(dI/dV) in monolayer-bilayer WSe₂.^[99] (d) Band alignment in monolayer-bilayer WSe₂ heterojunctions.^[99] (e) Selective subset of log(dI/dV) spectra. The green and red arrows represent valance and conduction band of the interface states.^[99]