Rhombohedral and Turbostratic Boron Nitride Polytypes Investigated by X-ray Absorption Spectroscopy

TL;DR

This study uses X-ray absorption spectroscopy and first-principles calculations to differentiate boron nitride polytypes and suggests that stacking variations can tune its band gap.

Contribution

It demonstrates the ability to distinguish BN polytypes via chemical shifts in X-ray absorption spectra and links stacking to band gap tuning.

Findings

Different BN polytypes show distinct chemical shifts in X-ray spectra.

Turbostratic BN exhibits a significant chemical shift at the B 1s-edge.

Band gap tuning is possible through stacking variations of BN polytypes.

Abstract

The electronic structure of rhombohedral sp2 hybridized boron nitride (r-BN) is characterized by X-ray absorption near-edge structure spectroscopy. Measurements are performed at the boron and nitrogen K-edges (1s) and interpreted with first-principles density functional theory calculations, including final state effects by applying a core-hole. We show that it is possible to distinguish between different 2D planar polytypes such as rhombohedral, twinned rhombohedral, hexagonal and turbostratic BN by the difference in chemical shifts. In particular, the chemical shift at the B 1s-edge is shown to be significant for the turbostratic polytype. This implies that the band gap can be tuned by a superposition of different polytypes and stacking of lattice planes.