Theoretical Prediction of Sliding Ferroelectricity in MoSiGeN₄ Bilayers

The advancement of out-of-plane ferroelectricity in two-dimensional (2D) materials is becoming increasingly significant due to their high potential for applications in miniaturized devices. Van der Waals (vdW) stacking has proven to be an effective technique for obtaining 2D ferroelectrics even from nonferroelectric parent compounds. Here, sliding ferroelectricity (SFE) in MoSiGeN4 bilayers, arranged in Si–Si and Ge–Ge configurations, is demonstrated through first-principles calculations based on density functional theory. SFE results from the breaking of the inversion symmetry due to interlayer sliding and is characterized by reversible out-of-plane polarization. By selecting a specific pathway, they exhibit lower interlayer sliding energy barriers (0.017 and 0.019 eV/f.u.) for ferroelectric switching, superior to some of the existing 2D SFE materials. The out-of-plane polarization of the Si–Si configuration (1.40 pC/m) is about two times greater than that of the Ge–Ge configuration (0.66 pC/m). Our results highlight the significance of low-dimensional ferroelectrics in vdW structures and could provide insights into the advancement of future devices.