Recently, piezoelectric characteristics have been a research focus for 2D
materials because of their broad potential applications. Black phosphorus
(BP) is a monoelemental 2D material predicted to be piezoelectric because of
its highly directional properties and non-centrosymmetric lattice structure.
However, piezoelectricity is hardly reported in monoelemental materials
owing to their lack of ionic polarization, but piezoelectric generation is con
sistent with the non-centrosymmetric structure of BP. Theoretical calcula
tions of phosphorene have explained the origin of piezoelectric polarization
among P atoms. However, the disappearance of piezoelectricity in multilayer
2D material generally arises from the opposite orientations of adjacent atomic
layers, whereas this effect is limited in BP lattices due to their spring-shaped
space structure. Here, the existence of in-plane piezoelectricity is experimen
tally reported for multilayer BP along the armchair direction. Current–voltage
measurements demonstrate a piezotronic effect in this orientation, and cyclic
compression and release of BP flakes show an intrinsic current output as
large as 4 pA under a compressive strain of
−
0.72%. The discovery of piezo
electricity in multilayer BP can lead to further understanding of this mecha
nism in monoelemental materials.
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