Fig. 5.

Thickness dependence of the coercive voltage (V_c) and coercive field (E_c) in BiFeO₃. (A) V_c vs. h, with TAFM data from all switched areas (closed blue circles), domain nuclei (open blue circles), and d₃₃-based measurements on macroscopic capacitor structures (black squares). Solid red line is a nonlinear power-law regression of V_c vs. h. (B) Logarithmic plot of E_c vs. h, using the same labeling convention as A. (Inset) Spectroscopic piezoresponse hysteresis loops (PFM phase) obtained at three discrete thicknesses following TAFM.