Hunting for Monolayer Boron Nitride: Optical and Raman Signatures

TL;DR

This paper presents methods to identify monolayer boron nitride using optical contrast and Raman spectroscopy, enabling accurate detection and layer counting despite its subtle optical signals.

Contribution

It introduces optimized viewing conditions and Raman signatures for reliable identification of monolayer BN, advancing material characterization techniques.

Findings

Monolayer BN has small optical contrast but is detectable with optimized viewing.

Raman spectroscopy shows an upshift of up to 4 cm-1 in the fundamental mode for monolayers.

Layer number can be determined by Raman intensity and optical contrast increments.

Abstract

We describe the identification of single- and few- layer boron nitride. Its optical contrast is much smaller than that of graphene but even monolayers are discernable by optimizing viewing conditions. Raman spectroscopy can be used to confirm BN monolayers. They exhibit an upshift in the fundamental Raman mode by up to 4 cm-1. The number of layers in thicker crystals can be counted by exploiting an integer-step increase in the Raman intensity and optical contrast.