Periodicity Dependence of the Built-in Electric Field in (Ba_0.7Ca_0.3)TiO₃/Ba(Zr_0.2Ti_0.8)O₃ Ferroelectric Superlattices

Symmetric ferroelectric superlattices consisting of (Ba_0.7Ca_0.3)TiO₃ (BCT) and Ba(Zr_0.2Ti_0.8)O₃ (BZT) layers were successfully grown on La_0.7Sr_0.3MnO₃ electroded (001)-oriented SrTiO₃ substrates by laser molecular beam epitaxy. With the monitor of reflective high-energy electron diffraction, the growth mode and rate were precisely controlled to realize the desired superlattice periodicity as confirmed by both X-ray diffraction and transmission electron microscopy results. The microscopic piezoelectric response and macroscopic ferroelectric properties were investigated as a function of periodicity of the BCTm/BZTm (m = 3, 5, 10, and 15 unit cells) superlattices. The existence of a built-in electric field was confirmed in all the superlattices and its strength was highly dependent on the periodicity. The excellent tunability of built-in electric field opens a path for designing microelectronic devices with various functionalities based on BCTm/BZTm superlattices.