Incorporation of specific defects through ion bombardment for better ferroelectrics

Incorporating specific defects into complex oxides facilitates the exploration of exotic phenomena and novel functionalities based on the intricate coupling between the defects and lattice/charge. However, methods for maximizing the density of specific defects while enhancing the desired properties have been rarely explored. In this study, the effect of N⁺ ion bombardment-driven specific defects on the properties of bismuth ferrite (BFO) thin films was investigated. Furthermore, atomic structure characterization and computational processing revealed the displacement and orientation of the Fe atoms, which are linearly related to the degree of polarization. The ion bombardment introduced deep-level trap states within the lattice, leading to a significant reduction in the leakage current and improved insulation performance of the films. By precisely engineering the defect content through N⁺ ion bombardment, the pure BFO thin films with remarkable and stable ferroelectric properties (remnant polarization, P_r = ∼116.8 µC·cm⁻²; leakage current, J = ∼1.5 × 10⁻⁸ A·cm⁻²) were fabricated. This innovative defect engineering-based approach enables the customization and optimization of local ferroelectric order parameters, thereby establishing a solid foundation for designing functionalities across various functional material systems.