Alternative Stacking Sequences in Hexagonal Boron Nitride

TL;DR

This study investigates different stacking sequences in hexagonal boron nitride, revealing that multiple stable configurations exist and introducing a scalable method to produce AB-stacked h-BN, which has distinct properties from the common AA' stacking.

Contribution

The paper combines theoretical analysis and experimental synthesis to identify and produce stable stacking sequences in h-BN, including a new scalable method for AB stacking.

Findings

AA' and AB stacking sequences have comparable low energy.

A scalable CVD method produces large AB-stacked h-BN flakes.

Different stacking sequences influence electronic and dielectric properties.

Abstract

The relative orientation of successive sheets, i.e. the stacking sequence, in layered two-dimensional materials is central to the electronic, thermal, and mechanical properties of the material. Often different stacking sequences have comparable cohesive energy, leading to alternative stable crystal structures. Here we theoretically and experimentally explore different stacking sequences in the van der Waals bonded material hexagonal boron nitride (h-BN). We examine the total energy, electronic bandgap, and dielectric response tensor for five distinct high symmetry stacking sequences for both bulk and bilayer forms of h-BN. Two sequences, the generally assumed AA' sequence and the relatively unknown (for h-BN) AB (Bernal) sequence, are predicted to have comparably low energy. We present a scalable modified chemical vapor deposition method that produces large flakes of virtually pure AB stacked h-BN; this new material complements the generally available AA' stacked h-BN.