Configuration and Charge Dynamics of Defect-Cluster-Dipoles in CaTiO3 for Enhanced Permittivity

Abstract

The wealth of complex defects induces attractive functionalities and structural variations in materials. This renders engineering defect states, as well as building up a defect-property relationship, a central subject, but it remains highly challenging because the configurations and charge dynamics of the involved defect systems are hardly explored and thus unclear experimentally. Herein, the defect-dipole-cluster in La-doped CaTiO₃ and, more importantly, its dielectric response process is clarified. Through combined HAADF-STEM, DFT calculation, dielectric, and photoluminescence (PL) spectroscopy, the defect configuration is identified to be V_Ca − O⁻ − La_Ca type defect-cluster-dipole. The electron–hole recombination from the Ti³⁺ and O⁻ states dominates the dielectric relaxation process, as revealed by the similar relaxation frequencies of dielectric response and photoluminescence emission. These findings experimentally demonstrate property tailoring involved in defect-cluster-dipole, providing crucial insights for establishing the defect-property relationship in dielectric materials.