Synthesis and intrinsic out-of-plane ferroelectricity of 2D Bi₂SiO₅

Two-dimensional (2D) ferroelectric materials demonstrate promising applications in nanoelectronics owing to their ultrathin thickness and spontaneous polarization. However, as the thickness decreases, ferroelectricity is often suppressed by depolarization effects, making 2D ferroelectric materials extremely scarce. Here, we report the intrinsic out-of-plane (OOP) ferroelectricity in 2D Bi₂SiO₅ (BSO) nanosheets. 2D BSO nanosheets were synthesized through a chemical vapor deposition (CVD) process, and their non-centrosymmetric structure was confirmed through second-harmonic generation (SHG) response. Switchable polarization and ferroelectric hysteresis loops in BSO nanosheets are revealed by piezo-response force microscopy (PFM) measurements. The ferroelectric switching behavior is further validated in a device made of a BSO nanosheet. The ferroelectricity in 2D BSO significantly expands the family of 2D ferroelectric materials and paves the way for their integration into nonvolatile memory devices.