Fig. 3: STEM mapping of tetragonality (c/a).

Two-dimensional mapping of c/a for L8B12S5 (a), L8B6S5 (c) and L8B2S5 (e). The corresponding c/a averaged within each atomic layer is plotted in (b), (d) and (f), respectively. The error bars show the standard deviation for each atomic plane. In (b), (d) and (f), the red line in upper panels indicates the c/a value of BTO single crystal, and the bottom panels show the HAADF intensity in arbitrary units for ease of identifying each layer.