Enhancement of giant piezoelectricity of group IV monochalcogenides through spontaneous compressive strain by layer stacking.

The piezoelectricity of group IV monochalcogenides has attracted much attention because their piezoelectric coefficients are orders of magnitude larger than those of other 2D materials. However, as the number of layers increases, their piezoelectric properties rapidly disappear because the natural stacking configuration, AB, cancels out the dipole moment of the monolayer. Here, using first-principles calculations, we investigated the giant piezoelectricity of group IV monochalcogenides in AA stacking, which has recently been stabilized in the experiments. Intriguingly, the observed piezoelectric coefficients of group IV monochalcogenides are much larger than those of any other reported layered materials, including their monolayer counterparts. The giant piezoelectricity of group IV monochalcogenides originates from their puckered structure, and can be further enhanced by the compressive strain spontaneously introduced during AA stacking. Our results suggest a novel way to optimize the piezoelectricity in low-dimensional materials.