Crack-Free Transfer of Wafer-Scale Freestanding Single-Crystalline Nanomembranes Enabled by Elastically Graded Polymer

Freestanding single-crystalline nanomembranes have gained increasing attention as promising platforms for both fundamental research and advanced electronic applications. However, internal stress gradients arising from epitaxial strain within the oxide membranes often result in high crack density during fabrication, leading to unsatisfactory yield and limited reliability. Here, an elastically graded polymer (EGP) support that enables wafer-scale crack-free transfer of single-crystalline oxide membranes are developed. The engineered elastic gradient within the EGP accommodates the internal strain of the oxide membrane, effectively minimizing crack formation during lift-off. Notably, this ability to spatially control the interfacial stiffness between the polymer and the oxide film enables crack suppression under both tensile and compressive strain. This approach provides a robust and scalable route to producing high-quality freestanding oxide membranes, paving the way not only for their integration into novel device architecture but also opening new avenues for scientific exploration of functional systems.