Dielectric phase transition and relaxor behavior in BaTiO3/LaNiO3 superlattice

Abstract

(001)-oriented BaTiO₃/LaNiO₃ superlattices with a symmetric structure were fabricated on LaNiO₃ buffered Si substrates. The formation of superlattice was confirmed by X-ray diffraction and transmission electron microscope observations. In contrast to the sharp dielectric transition of pure bulk BaTiO₃, a broad dielectric anomaly with shift in dielectric maxima toward higher temperature with increasing frequency is observed, suggesting the system exhibits diffusive phase transition following the Vogel–Fulcher relationship. Furthermore, with decreasing stacking periodicity, out-of-plane lattice constant of the superlattice is increased, room temperature dielectric constant is enhanced, while phase transition temperature is decreased. The observed structure-dielectricity correlation is attributed to both strain effect of the inserted LaNiO₃ layer and the interfacial Maxwell–Wagner effect.