A Novel Multiple Interface Structure with the Segregation of Dopants in Lead-Free Ferroelectric (K_0.5Na_0.5)NbO₃ Thin Films

Interfaces in oxides are found to possess different properties and can be engineered for modifying local structure and properties of nearby area. In this work, it is reported that the interfaces can be formed in Ba/Zr (BZ)-doped (K,Na)NbO₃ (KNN) thin films by cycles of chemical solution deposition using same precursor solution. In the films, a novel and special cross-sectional structure is observed with periodic distribution of Ba-rich and Zr-rich layers. The Ba-rich and Zr-rich layers exhibit different strain, lattice parameters, and crystal structure, leading to an obvious effect on the general ferroelectric properties of the KNN-based thin films. Moreover, the self-polarization is also observed, which can be understood to originate from the formed built-in field by layered distribution of Ba and Zr in the KNN-BZ thin films.