Tuning Self-Polarization of Epitaxial BiFeO₃ Thin Films through Interface Effects

Interface effects and strain engineering have emerged as critical strategies for modulating polarization and internal electric fields in ferroelectric materials, playing a vital role in exploring coupling mechanisms and developing ferroelectric diode devices. In this study, we selected BiFeO₃ as a representative ferroelectric material and utilized interface engineering to control its polarization. By precisely manipulating the atomic stacking sequence at the interface, we influenced the electrostatic potential step across the interface, resulting in a bias voltage in the ferroelectric hysteresis loops that defined the ferroelectric state. The introduction of strain and strain gradients through a lattice mismatch between the film and substrate generated a flexoelectric field of approximately 3 MV/m, significantly impacting the internal electric field. Additionally, we successfully modified the Schottky barrier height within BiFeO₃ films through the synergy and competition between interfacial and flexoelectric effects. This work expands the potential applications of thin-film flexoelectricity in Schottky diodes, sensors, and memory devices.