Tuning ferroelectricity by charge doping in two-dimensional SnSe

Abstract

Tuning ferroelectricity in two-dimensional (2D) ferroelectric materials is important for future applications. Using first-principles calculations, we show that charge doping is an effective way of tuning the ferroelectricity of group IV monochalcogenides MX (M = Ge, Sn; X = S, Se). Our calculations show that hole doping can decrease and even turn off ferroelectricity in SnSe. This can be explained by the change in strengths of in-plane bonds and out-of-plane bonds in this material. In addition, we find that charge doping can effectively change the lattice constants of MX. This indicates that these materials may be good substrates for constructing van der Waals heterojunctions with other 2D materials, in which the moiré pattern can be effectively tuned by doping electrons and holes.