Large‐Area Release of Pb(Zr, Ti)O ₃ Films With Reduced Crack Generation via Ferroelastic Domain Engineering

Crack‐free freestanding ferroelectric membranes with thicknesses exceeding 100 nm are highly desirable for flexible electronics and optical applications. Here, we report the release and transfer of 200 nm‐thick Pb(Zr, Ti)O ₃ (PZT) films enabled by ferroelastic domain engineering via thermal expansion mismatch, without the use of any capping or covering layers. In contrast to PZT films grown on Sr ₃ Al ₂ O ₆ (SAO)/SrTiO ₃ (STO) substrates, which exhibit mixed c / a / c / a ‐domain structures and severe cracking during release process, PZT films deposited on CaF ₂ substrates undergo compressive strain upon cooling, stabilizing a single c ‐domain configuration and effectively eliminating residual stress. By integrating a newly developed STO/(La, Sr)(Al, Ta)O ₃ double buffer layer, a water‐soluble SAO sacrificial layer was successfully intergraded on CaF ₂ , enabling large‐area release by simple immersion in water. The transferred PZT membranes retain robust piezoelectric and ferroelectric responses without any structural or functional degradation. This strategy provides a general and scalable pathway for realizing thick, crack‐free ferroelectric membranes for flexible and freestanding functional devices.