Charge distribution across dislocation networks induced by a strained top layer in hexagonal boron nitride substrates

TL;DR

This paper investigates how strain-induced dislocation networks in hexagonal boron nitride create piezoelectric charge hotspots that affect the electrostatic environment of encapsulated 2D materials.

Contribution

It provides a detailed analysis of charge distribution caused by dislocation networks in strained hBN, revealing their role as charged defect-like electrostatic modulations.

Findings

Dislocation networks generate piezoelectric charge hotspots.

Strain and twist induce lattice reconstruction in hBN.

Charge hotspots act as charged defects affecting 2D materials.

Abstract

Hexagonal boron nitride (hBN) flakes are key building blocks for encapsulating two-dimensional (2D) materials, providing atomically flat surfaces and an excellent dielectric environment for high-mobility field-effect transistors and tunnelling devices. However, strain induced during mechanical exfoliation and assembly of van der Waals heterostructures may lead to plastic deformations of the hBN surface, injecting dislocation lines between the topmost layer and the underlying film. Since a monolayer of hBN is non-centrosymmetric and exhibits a piezoelectric response to deformation, individual dislocations and, in particular their networks, can generate electrostatic potential modulations in the encapsulated 2D material. Here, we examine scenarios in which the top hBN layer is uniaxially strained and/or twisted, and show how lattice reconstruction into dislocation networks leads to the formation of piezoelectric charge hotspots that effectively behave as charged defects.