Origin of the excitonic recombinations in hexagonal boron nitride by spatially resolved cathodoluminescence spectroscopy

TL;DR

This study uses spatially resolved cathodoluminescence spectroscopy to identify the origins of different excitonic recombinations in hexagonal boron nitride, linking specific emissions to defect-rich regions.

Contribution

It provides new insights into the spatial distribution of excitonic emissions in hBN and associates defect-related emissions with structural imperfections.

Findings

215 nm emission is homogeneously distributed

220 nm and 227 nm emissions are localized in defect-rich regions

Defect-related emissions are linked to crystalline imperfections

Abstract

The excitonic recombinations in hexagonal boron nitride (hBN) are investigated with spatially resolved cathodoluminescence spectroscopy in the UV range. Cathodoluminescence images of an individual hBN crystallite reveals that the 215 nm free excitonic line is quite homogeneously emitted along the crystallite whereas the 220 nm and 227 nm excitonic emissions are located in specific regions of the crystallite. Transmission electron microscopy images show that these regions contain a high density of crystalline defects. This suggests that both the 220 nm and 227 nm emissions are produced by the recombination of excitons bound to structural defects.