Programmable Piezoelectricity of 2D Hexagonal Boron Nitride via Defect Engineering

Piezoelectricity in 2D hexagonal boron nitride (hBN) plays a crucial role in its applications in various advanced functional devices. Therefore, appropriately adjusting intrinsic piezoelectric properties of 2D hBN becomes desirable for different advanced piezoelectric applications. Herein, using the Kelvin probe force microscope, it is directly found that local piezoelectric potentials of monolayer hBN can be enhanced by ≈20% after the introduction of defects. High-throughput molecular dynamics simulations on hundreds of thousands of defective 2D hBN structures further show a continuous decrease or even increase in piezoelectric coefficients by properly designing the defect structures. The tunability of piezoelectricity in defective 2D hBN is found to be mainly attributed to flexoelectric effects around defects, which can increase or reduce the polarization in stretched defective 2D hBN by over 50%. To inversely design defective 2D hBN structures with specific piezoelectric properties, a machine learning-based method is proposed. Besides hBN, the proposed defect engineering strategy also has the capacity to be extended to tailor the piezoelectric properties of other 2D materials, such as molybdenum disulfide. This work not only expands the understanding of piezoelectricity in defective 2D hBN but also offers a novel approach to designing the piezoelectric property of 2D materials via defect engineering.