Interlayer sliding induced antiferroelectricity–ferroelectricity–antiferroelectricity transition in bilayer δ-SiX (X = S/Se)†

Two-dimensional (2D) sliding ferroelectric materials possess intriguing physical and electronic properties, thereby greatly expanding the family of 2D ferroelectrics (FEs). In this work, using first-principles calculations, we demonstrate a reversible antiferroelectricity–ferroelectricity–antiferroelectricity (AFE–FE–AFE) transition in bilayer δ-SiX (X = S/Se) along the in-plane direction during interlayer sliding. This transition primarily stems from the mechanical sliding of the top layer. Notably, spontaneous polarization (P_s) can reach up to approximately 80 pC m⁻¹ and 70 pC m⁻¹ for bilayers SiS and SiSe, respectively. Furthermore, the mechanism underlying this phase transition involves the interlayer between interaction energy (E_inter) and strain energy (E_ε). In the case of bilayer SiS, along the AB_AFE–AA_FE–AB_AFE path, critical points arise from the cooperation of strain energy and mechanical sliding force. During the AC_AFE–AD_FE sliding process, phase transition relies on the combined effect of strain energy and mechanical sliding force. At the AD_FE–AC_AFE point, the transition is primarily driven by the combined action of interlayer interaction energy and mechanical sliding force. This theoretical work not only establishes a feasible approach for achieving a reversible AFE–FE–AFE phase transition, but also offers valuable insights for the design of novel volatile devices.