Polarization in the van der Waals-bonded graphene/hBN heterostructures with triangular pores

This study investigates the effect of strain gradient on polarization with non-centrosymmetric triangular pores in graphene and hexagonal boron nitride (hBN) nanosheets heterostructure using density functional theory (DFT). Two-dimensional (2D) nanosheets, like hexagonal boron nitride and graphene, are vertically stacked to create a new class of materials called van der Waals (vdW) heterostructures. These heterostructures have distinctive and highly controllable electrical characteristics. The change in the piezoelectric coefficient due to the change in graphene layers is analyzed using DFT. Firstly, the polarization of bilayer graphene with non-centrosymmetric triangular holes has been determined by applying an axial load. Further, variation in polarization with an increment in graphene layers and its heterostructure with hBN nanosheets has been studied with the help of the quantum electrostatic heterostructure (QEH) model. The QEH model has been implemented to reduce computational efforts, and it was found to be reliable with the results obtained using the first principles. Additionally, the polarization properties of different heterostructure configurations have been evaluated. It was found that strain-induced polarization in graphene heterostructure with non-centrosymmetric defects is a nanoscale phenomenon that converts non-piezoelectric graphene into piezoelectric graphene. The calculations are performed using the real-space, grid-based projector-augmented wave (GPAW) DFT method and the QEH model. These models were implemented in python script. The work presented in this paper signifies the importance of slight tweaking of pores and heterostructure layering, which can help achieve improvements in piezoelectric properties that, in turn, have tremendous application in nanoelectromechanical systems (NEMS).