(a) Crystal structure of β-Bi. Red and blue colors label the upper and lower atomic layers of the topmost bilayer, respectively. Here, bilayer means two (upper and lower) atomic layers. (b) Topography around the hexagonal pit-like defect, differential conductance is shown with color plot, showing high conductance at alternative edges.^[89] (c) STS of the step edge (blue) and the inner terrace (red) of Bi/Bi₂Te₃ island averaged over the area as marked in the inset of (c). The STS, the bands aligned Dirac point “DP” as indicated by the blue dashed line. The orange dashed lines mark the band gap of the topmost Bi layer.^[3] (d) Differential conductivity dI/dV at different distances from the edge. A large gap of ∼ 0.8 eV is observed in bulk bismuthene (black curve). Inset shows the STS measurement locations at uphill substrate step causing the boundary.^[4]