Quantification of internal electric fields and local polarization in ferroelectric superlattices

Oxide heterostructure superlattices constitute a new family of materials with tunable ferroelectric properties. While theoretical models predict the presence of nanosized ferroelectric domains in these films, they had not been observed as the magnitude of the response functions challenges the limits of experimental detection. Here, a new protocol in a precise variant of piezoforce microscopy is used to image domains in BaTiO₃/SrTiO₃ superlattices. Comparison of experimentally determined polarization to predictions of phase-field calculations is in quantitative agreement. Additionally, a combination of theory and experiment is used to determine the magnitude of internal electric field within the thin film, in a procedure that can be generalized to all ferroelectric films.