Robust ferroelectricity in low-dimensional δ-SiX (X = S/Se): a first-principles study

Low-dimensional ferroelectric materials hold great promise for application in nonvolatile memory devices. In this work, ferroelectricity in two-dimensional monolayers and one-dimensional nanowires based on δ-SiX (X = S and Se) materials with spontaneous polarization and ferroelectric switching energy barriers has been predicted using the first-principles method. The results show that the intrinsic ferroelectric values due to spontaneous polarization of 2D-SiS, 2D-SiSe, 1D-SiS and 1D-SiSe are 3.22 × 10^-10 C m^-1, 3.00 × 10^-10 C m^-1, 7.58 × 10^-10 C m^-1 and 6.81 × 10^-10 C m^-1, respectively. The Monte Carlo simulations and ab initio molecular dynamics (AIMD) simulations both indicate that 2D-SiX and 1D-SiX exhibit room-temperature ferroelectricity. Moreover, the polarization and ferroelectric switching energy barrier can be tuned by applying a strain. Notably, spontaneous spin polarization can be achieved by hole doping in one-dimensional nanowires. Our findings not only broaden the research field of low-dimensional ferroelectric materials, but also provide a promising platform for the application of novel nano-ferroelectric devices.