Fig. 4. CG-TC SECCM imaging of carrier transport across an individual step edge defect within an n-WSe₂ nanosheet. (a) Photocurrent images at a series of different applied potentials (1 µm resolution). (b) Optical transmission image of the n-WSe₂ nanosheet with the area imaged via SECCM and locations of the AFM height profiles indicated. (c) AFM height profiles of the n-WSe₂ nanosheet. (d) Cross-sections of the SECCM photocurrent images given in (a). SECCM data was acquired using a pipet (d = 250 nm, θ_p = 8.5°) filled with an aqueous solution containing 100 mM NaI, 10 mM I₂ at a sweep rate of 2000 mV s⁻¹. Imaging was carried out in the vicinity of a 633 nm Gaussian beam with P₀ = 600 nW and σ₀ = 0.73 µm.