Thickness and electrode effects on thermally stable 0.5BiFeO3-0.5BaTiO3 lead-free epitaxial thin films with large polarization

The development of ferroelectric thin films is largely driven by their potential applications in microelectronic devices. However, as ferroelectrics are thinned, the effects of thickness and electrodes on their functional properties are significant. Understanding these properties is critical for future engineering of novel ferroelectric devices. Here, we demonstrate that large epitaxial compressive strain can lead to substantial enhancement of lattice parameter ratio c/a and ferroelectric polarization in (1– x )BiFeO 3 - x BaTiO 3 ( x = 0.5) thin films, values of which are much larger than those in the bulk. Notably, saturated P – E loops with a polarization exceeding 100 μC/cm 2 are maintained even when the temperature reaches 200 °C by an electrode engineering, which is rarely achieved in perovskite ferroelectrics with such a high polarization level. As the thickness increases, the weakening of the asymmetric electrode effect and the lattice relaxation can induce the transformation of off-center single P – E loops into pinched P – E loops in the presence of defect dipoles, while symmetric electrodes induce pinched P – E loops in the films. Our findings underscore the significant potential of strained BiFeO 3 -BaTiO 3 epitaxial films in ferroelectric devices.