Toward damage-free freestanding oxide membranes: Defects formation mechanisms and mitigation strategies

Freestanding oxide membranes have emerged as a versatile platform for oxide electronics, semiconductor integration, flexible devices, energy and quantum technologies. Despite rapid progress in membrane synthesis and properties exploration, achieving large-area damage-free freestanding oxide membranes remains a critical challenge due to the intrinsic mechanical fragility and potential damage induced by the multi-step membrane synthesis and transfer processes. In this review, we summarize the current strategies for fabricating damage-free freestanding oxide membranes, with a particular emphasis on the sacrificial layer-assisted wet chemical etching method. The fabrication workflow is systematically divided into four key stages: epitaxial thin-film growth, polymer support layer application, sacrificial layer dissolution and lift-off, and membrane transfer. The defects formation mechanisms and suppressing strategies during each processing stage is thoroughly discussed. This review aims to provide a comprehensive practical guideline for the processing of high-quality freestanding oxide membranes and to accelerate their integration into future electronic and multifunctional devices.