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Figure 3. Hidden ferroelectricity of CaTiO₃ and oxygen octahedra pattern engineering. (A) Annular bright field (ABF)-STEM and piezoresponse force microscopy (PFM) analysis of paraelectric CaTiO₃ on (001) LaAlO₃. Corresponding oxygen octahedral rotation mapping and polarization mapping results coincident with the non-polar structure. (B) ABF-STEM and PFM analysis of ferroelectric CaTiO₃ on (111) LaAlO₃. Corresponding oxygen octahedral rotation mapping, and polarization mapping results coincident with the polar structure. Reproduced with permission^[70]. Copyright 2020, The Authors, published by Springer Nature.