Water-Assisted Exfoliation of HfO₂-Based Membrane for Flexible Robust Ferroelectric Synaptic Transistors

HfO₂-based thin films possess broad application potential in semiconductors, non-volatile memory, and neuromorphic computing owing to their high dielectric constant, excellent ferroelectricity, and environmental robustness. However, an environmentally friendly strategy for synthesizing flexible HfO₂-based films remains lacking. In this work, by incorporating a BaTiO₃/Hf₀.₅Zr₀.₅O₂/BaTiO₃ (BTO/HZO/BTO) sandwiched architecture together with a Sr₄Al₂O₇ sacrificial layer, a freestanding HfO₂-based heterostructure can be detached simply by applying pure water. The resulting film exhibits high film quality and stable ferroelectric behavior, along with pronounced flexibility that enables repeated transfer onto diverse substrates. Furthermore, the synthesized freestanding film is employed to construct a ferroelectric field-effect transistor that successfully emulates synaptic functionalities, highlighting its potential for low-power neuromorphic hardware. This work provides a viable strategy for developing high-performance artificial synapses based on flexible oxide heterostructures.