Pseudo-substrate boost layer-enabled integration of mixed-phase BiFeO3 on silicon

Ferroelectric oxides have attracted considerable attention due to their unique intrinsic properties, such as spontaneous polarization and high dielectric constants, which make them promising candidates for nonvolatile memory devices, electrostrictive actuators, and sensors. However, integrating ferroelectric oxides with silicon remains a significant challenge, hindering their widespread use in nanoelectronic devices. Here, we introduce a fully strain-relaxed boost layer that functions as a pseudo-substrate, enabling the integration of multiferroic mixed-phase BiFeO3 (BFO) on silicon. This boost layer not only overcomes the limitations of traditional single-crystal oxide substrates by providing a strain platform but also facilitates the stabilization of BFO mixed phases through strain engineering. Additionally, we demonstrate that an external electric field can reversibly switch between these two phases and toggle between distinct polarization states. These results highlight a strain-engineering strategy that advances ferroelectric oxide integration with semiconductor platforms, paving the way for scalable and cost-effective device applications.