Fig. 3: Observation of polar Bloch points in a trilayer SRO/PTO/SRO thin film grown on the SSO substrate.
a The 3D sketch of the low-magnification planar-view TEM image overlaid with the cross-sectional dark-field TEM images, displaying the overview of the film. b Superposition of reversed Ti-displacement vectors (−δTi) and the atomic-resolved HAADF-STEM image. The −δTi vectors of PTO unit cells were shown as yellow arrows. c Magnified −δTi vector maps showing four typical polarization patterns marked as “1”–“4” in the thin film corresponding to four red boxes labeled as “I”–“IV” in b, respectively. d Atomic-resolved HAADF-STEM image and EDS mapping of the region in the red box labeled as “V” in b showing the sharp interfaces of SRO/PTO and PTO/SRO. e The −δTi vector map based on the atomic-resolved planar-view HAADF-STEM image, showing the convergent polarization patterns (black circles) at head-to-head domain walls (black lines). The arrows with different colors denote the polarization directions of PTO unit cells. f The magnified −δTi vector map of a typical convergent polarization pattern corresponding to the area in e.
