Figure 5

PFM phase (a) and amplitude (b) images along with the AFM topography image (c) taken on the (111) surface of Sample #2 over the area marked by a yellow dashed rectangle in Fig. 4(a). Panels (d–f) present the corresponding profiles along the same line indicated by white bars in panels (a–c). The alternating yellow-red backgrounds of the line profiles indicate domains distinguishable by the AFM topography and PFM measurements. The difference in the surface inclination angle in adjacent domains, denoted as γ, is displayed by a blue arc in panel (f). Panel (g) shows the polarization directions in the four rhombohedral domains in a single inversion variant of the crystal. Red and yellow colors represent the different sign and magnitude of the out-of-plane PFM signal observable on the (111) surface. Panel (h) presents the only compatible solution that yields PFM contrast, as observed along the line profile. The top image shows the in-plane and out-of -plane polarization vectors with reference to the scanning directions. The bottom image displays the three-dimensional structure of this solution with the color coding corresponding to panels (d–g).