Emergence of sliding ferroelectricity in reduced-size SnS nanoparticles

Nano-ferroelectrics have great potential for nanoelectronic applications, the depolarization field causes the ferroelectric polarization to diminish or even disappear with decreasing size, and it remains a challenge to maintain ferroelectricity at small sizes. Here we report the emergence of sliding ferroelectricity in 6 nm SnS nanoparticles. The interlayer sliding was observed using scanning transmission electron microscopy, while the emergence of ferroelectricity was confirmed through second harmonic generation and piezoelectric force microscope. Further local structural investigations of atomic pair distribution functions exposed the atomic layer-to-layer sliding subjected to 3.4% compressive strain, and the inhomogeneous offset of atomic arrays, which generate the correlation change of interlayer stacking.Interlayer sliding allows one to realize the reversal of ferroelectricity according to density functional theory calculations. Our research reveals that non-ferroelectric SnS undergoes 3.4% compressive strain when its size is reduced to 6 nm, which induces sliding ferroelectricity, and overcomes the limitations associated with the size effect in ferroelectrics. This finding enables non-ferroelectric materials to exhibit ferroelectric properties, extends the scope of sliding ferroelectrics to nanoparticles, provides new insights into the discovery of ferroelectrics, and presents a candidate material for use in nano-optoelectronic devices.