Fig. 3: Evaluation using grain boundaries in the WS2 region.
a STM topographic image and images of currents Is and Id flowing into of the source and drain electrodes on the sample (Vs = −6 V, Iset = 5 pA), respectively. Each image consists of 128 horizontal line scans. The light spot size was about 20 μm and the area was illuminated almost entirely. No apparent overlayers with a triangular shape were not observed in the illuminated area. Red triangles indicate the left side edge. See Supplementary Fig. 2 about the GB structures. b Schematic diagram of the relationship between the STM tip position and the current obtained at the source and drain electrodes. c Steplike change and the spatial derivative obtained from the plot of Is in a. The values were averaged over a ±15 nm area from the interface. d, e Electric field and exciton binding energy dependences of S for WS2 and WSe2, respectively. f Cross-sections along the broken lines shown in d (Eb = 0.28 eV) and e (Eb = 0.31 eV).
