Giant ferroelectric polarization and multiferroicity of two-dimensional hydrofluorinated SiC

Two-dimensional (2D) multiferroic materials are crucial for designing next-generation functional devices. However, 2D multiferroic materials remain extremely scarce, particularly ferroelectric–ferroelastic materials. Based on the RG2 structure search algorithm and first-principles calculations, we systematically study the hydrogenated (fluorinated) monolayer SiC and find that the α-phase structures have the lowest energy and possess good stability. Interestingly, the polarization value of α-H-SiC-H is as high as 10.61 × 10−10 C/m, which is the largest polarization value discovered in 2D materials to date. It is found that due to the unique symmetry and large Poisson's ratio of α-X-SiC-X (X = H, F), under tensile (compressive) strain along the zigzag (armchair) direction, the structure can achieve a 90° lattice rotation, leading to a switch in the polarization direction, thereby realizing ferroelastic–ferroelectric multiferroicity. Moreover, its ferroelectricity can be maintained at temperatures up to 500 K. Our study not only proposes a class of highly promising 2D multiferroic materials but also demonstrates that the functionalization of 2D materials may be one of the effective methods for inducing their multiferroic properties.