Preferential 90° Strain-Induced Polarization Switching by Engineering In-Plane Symmetry

Switchable polarization makes ferroelectrics a critical component in memories, actuators, and electro-optic devices, and potential candidates for nanoelectronics. A strain-induced preferential 90° polarization switching in ferroelectric oxides is highly desirable for achieving enhanced electromechanical response. However, such strain-induced switching typically proceeds along random paths under tensile strain in two opposite directions, which is unfavorable for electromechanical device performance. Here, we propose a strategy that leverages miscut-angle-driven in-plane symmetry breaking to preferentially control the 90° polarization switching path in freestanding PbTiO₃ (PTO) films under uniaxial strain. Theoretical calculations highlight the key role of miscut substrates in manipulating the energy landscape during strain engineering. A combination of in situ X-ray diffraction and vector piezo-response force microscopy measurements directly reveals that preferential 90° polarization switching can be achieved by engineering in-plane symmetry. This work establishes design principles for controlling 90° polarization switching paths in freestanding ferroelectric oxides for high-performance electromechanical devices.