Fig. 11: Thin-film engineering approaches that induce or enhance ferroelectricity in perovskite thin-film and superlattices.

Figure schematically shows that the ferroelectric polarization can be induced or enhanced by applied external strain as discussed, chemical compositions that breaks inversion symmetry in tricolor superlattices, electrostatic interaction mediated by the interfaces in the superlattices, and structural reconstruction associated with oxygen octahedron, which are discussed in the section of “Ferroelectricity in thin films under epitaxial strain”, “Compositional inversion symmetry breaking”, “Electrostatic coupling effect via interfaces”, and “Interfacial reconstructions of structural instabilities”, respectively.