Engineering piezoelectricity at vdW interfaces of quasi-1D chains in 2D Tellurene.

Low-dimensional piezoelectrics have drawn attention to the realization in nano-scale devices
with high integration density. A unique branch of 2D Tellurene bilayers formed of weakly
interacting quasi-1D chains via van der Waals (vdW) forces is found to exhibit piezoelectricity due
to the semiconducting band gap and spatial inversion asymmetry. Various bilayer stackings are
systematically examined using density functional theory (DFT), revealing optimal piezoelectricity
when dipole arrangements are identical in each layer. Negative piezoelectricity has been observed in
two of the stackings AA' and AA" while other two stackings exhibit the usual positive piezoelectric
effect. The layer-dependent 2D piezoelectricity (| e 2D 22 |) increases with an increasing number of
layers in contrast to the odd-even effect observed in h-BN and MoS 2 . Notably, the piezoelectric
effect is observed in even-layered structures due to the homogeneous stacking in multilayers. Strain
is found to enhance in-plane piezoelectricity by 4.5 times (-66.25 × 10 -10 C/m at -5.1% strain) due
to the increasing difference in Born effective charges (BECs) of positively and negatively charged
Te-atoms under compressive biaxial strains. Moreover, out-of-plane piezoelectricity is induced by
applying an external electric field, thus implying Tellurene is a promising candidate for piezoelectric
sensors.