Fig. 2: Local polar structure of NN-P1.

Bright-field TEM images, high-resolution TEM images and the corresponding SAED patterns: along the a–c [110]c, d–f [100]c directions of NN-P1; g Atomic-resolution polarization vector mapping according to the HAADF-STEM image along [100]c. The accompanied statistic distribution of h magnitude and i angle of the polarization vectors. j Polarization magnitude mapping, and k Polarization angle mapping.