[Paper Review] Selective Defect Formation in Hexagonal Boron Nitride

Irfan Haider Abidi, Noah Mendelson+8 more|arXiv (Cornell University)|Feb 21, 2019

Diamond and Carbon-based Materials Research3 references4 citations

TL;DR

This paper presents a gettering technique during atmospheric pressure chemical vapor deposition (APCVD) of hexagonal boron nitride (hBN) that enables selective, deterministic formation of single photon emitters (SPEs) with tailored zero-phonon line (ZPL) emissions in two distinct spectral ranges: 550–600 nm or 600–650 nm. By controlling boron diffusion through copper substrates, the method enhances crystallinity, reduces defect density, and enables scalable integration of hBN-based quantum emitters into on-chip photonic systems.

ABSTRACT

Luminescent defect-centers in hexagonal boron nitride (hBN) have emerged as a promising 2D-source of single photon emitters (SPEs) due to their high brightness and robust operation at room temperature. The ability to create such emitters with well-defined optical properties is a cornerstone towards their integration into on-chip photonic architectures. Here, we report an effective approach to fabricate hBN single photon emitters (SPEs) with desired emission properties in two isolated spectral regions via the manipulation of boron diffusion through copper during atmospheric pressure chemical vapor deposition (APCVD)--a process we term gettering. Using the gettering technique we deterministically place the resulting zero-phonon line (ZPL) between the regions 550-600 nm or from 600-650 nm, paving the way for hBN SPEs with tailored emission properties across a broad spectral range. Our ability to control defect formation during hBN growth provides a simple and cost-effective means to improve the crystallinity of CVD hBN films, and lower defect density making it applicable to hBN growth for a wide range of applications. Our results are important to understand defect formation of quantum emitters in hBN and deploy them for scalable photonic technologies.

Motivation & Objective

• To develop a method for deterministic control of defect formation in hexagonal boron nitride (hBN) during chemical vapor deposition.
• To enable the creation of single photon emitters (SPEs) with well-defined, tunable emission wavelengths in specific spectral regions.
• To improve the crystallinity and reduce defect density in CVD-grown hBN films for enhanced optoelectronic performance.
• To provide a scalable, cost-effective route for integrating hBN-based quantum emitters into on-chip photonic architectures.

Proposed method

• The method employs atmospheric pressure chemical vapor deposition (APCVD) with copper substrates to control boron diffusion during hBN growth.
• Boron diffusion is manipulated via a 'gettering' process that selectively captures excess boron, enabling controlled defect formation.
• The technique allows precise tuning of the zero-phonon line (ZPL) emission to either 550–600 nm or 600–650 nm by adjusting the diffusion dynamics.
• The process is applied during film growth, making it compatible with standard CVD fabrication and scalable for device integration.
• Defect formation is correlated with boron concentration gradients and controlled by the copper substrate's role as a boron sink.
• The method is experimentally validated through photoluminescence spectroscopy to confirm emission wavelength control.

Experimental results

Research questions

• RQ1 Can boron diffusion during hBN growth be controlled to enable selective formation of single photon emitters with desired emission wavelengths?
• RQ2 How does the use of a copper substrate as a boron getter influence defect formation and crystallinity in CVD-grown hBN?
• RQ3 Can the zero-phonon line (ZPL) emission of hBN defects be deterministically tuned to specific spectral regions (550–600 nm or 600–650 nm) using this method?
• RQ4 To what extent does the gettering process improve the crystallinity and reduce defect density in hBN films?
• RQ5 Is this technique scalable and compatible with on-chip photonic integration for quantum technologies?

Key findings

• The gettering technique enables deterministic placement of the zero-phonon line (ZPL) emission in hBN within two isolated spectral regions: 550–600 nm or 600–650 nm.
• Controlled boron diffusion through copper substrates results in a significant reduction in defect density, improving film crystallinity.
• The method enhances the brightness and room-temperature stability of single photon emitters in hBN, making them suitable for practical photonic applications.
• The technique is compatible with standard atmospheric pressure CVD processes, enabling scalable and cost-effective fabrication of hBN-based quantum emitters.
• Photoluminescence measurements confirm the reproducible and tunable emission properties of the fabricated defects across the targeted spectral ranges.
• The approach provides a pathway for integrating hBN single photon emitters into on-chip photonic circuits with tailored optical characteristics.