Chemical Vapor Deposition Growth of Two-Dimensional Bi4Se3 with Robust Ferroelectricity

Bi4Se3 is a topological superlattice material that has been extensively studied for applications in catalysis, photovoltaics, and thermoelectrics. However, existing methods typically yield Bi4Se3 polycrystalline films with nonhomogeneous phases, significantly limiting their use in electronic devices. In this study, we demonstrate the chemical vapor deposition (CVD) growth of two-dimensional (2D) single-crystal Bi4Se3 with a lateral size up to 20 μm and a thickness as thin as 4 nm. The growth process involves the formation of a Bi2O2 layer, which promotes the development of [Bi2Se3·Bi2Ox] and facilitates the release of oxygen atoms at elevated temperatures. Notably, optical second harmonic generation (SHG) characterization reveals the noncentrosymmetric structure of the 2D Bi4Se3. Furthermore, at room temperature, switchable out-of-plane ferroelectric polarization was observed in 2D Bi4Se3. Finally, double-ended memory resistor measurements of the Bi4Se3-based device demonstrate a large switching ratio of approximately 104 within a voltage range of 2.5 V and a retention time exceeding 270 s. This work provides a method for synthesizing single-crystal Bi4Se3 and highlights its robust ferroelectricity, offering potential for applications in ferroelectric nonvolatile devices.