Figure 3

PFM phase (a) and amplitude (b) images along with the AFM topography image (c) taken on the (001) surface of Sample #1 over the area marked by a yellow dashed rectangle in Fig. 2(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 the 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 of the out-of-plane PFM signal observable on the (001) surface. Panel (h) presents one of the two possible compatible solutions for the observed alternating structure along the line profile. The top image shows the in-plane and out-of plane polarization vectors with reference to the scanning directions and the alternating electric field applied by the PFM tip, denoted by E^ω. The bottom image illustrates the three-dimensional structure of this solution with the color coding corresponding to panels (d–g).