Probing Correlation of Optical Emission and Defect Sites in Hexagonal Boron Nitride by High-Resolution STEM-EELS

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Optics

Background:

• Hexagonal boron nitride (hBN) exhibits optically bright emitters, often functioning as single-photon sources.
• These emitters are typically linked to point-defect centers with localized electronic states.
• The precise nature of most visible-spectrum single-photon emitters (SPEs) in hBN remains unidentified, with vacancies, anti-sites, and impurities being proposed candidates.

Purpose of the Study:

• To resolve and identify the physical and chemical nature of single-photon emitters in hexagonal boron nitride.
• To investigate the role of specific defects in visible-spectrum optical emission from hBN.
• To provide insights for the controlled fabrication of efficient emitters in hBN.

Main Methods:

• Combined site-specific high-angle annular dark-field imaging (HAADF) with electron energy loss spectroscopy (EELS).
• Utilized first-principles calculations to assess defect stability and optical transitions.
• Correlated experimental observations of optical emission with identified defect structures.

Main Results:

• Identified carbon substitutions within neighboring hBN hexagons as a source of typical defect emission.
• Observed these carbon defects within the same sample region exhibiting optical emission.
• First-principles calculations supported the stability and optical transition properties of the proposed carbon-defect complex.

Conclusions:

• Carbon complexes are a probable cause of visible single-photon emission in hexagonal boron nitride.
• The study establishes a direct correlation between observed optical emission and specific carbon defects.
• This work offers valuable information for the controlled engineering of single-photon emitters in hBN.