Defect Engineering in Large‐Scale CVD‐Grown Hexagonal Boron Nitride: Formation, Spectroscopy, and Spin Relaxation Dynamics

Why It Matters

Controlled defect engineering in CVD‑grown hBN enables deterministic quantum photonic device fabrication, accelerating the transition from lab‑scale prototypes to commercial quantum technologies.

Key Takeaways

• Ion type dictates boron vacancy formation
• Substrate introduces secondary particles, complicating defects
• 800 nm emission signals V_B⁻ defects
• Defect density controls spin relaxation times
• Optical and ODMR methods differentiate defect species

Pulse Analysis

Hexagonal boron nitride (hBN) has emerged as a leading host for solid‑state quantum emitters because its wide bandgap supports stable, room‑temperature single‑photon sources. While exfoliated flakes can be manually defect‑engineered, commercial adoption demands large‑area, chemically vapor‑deposited (CVD) films that can be processed on wafer scales. The principal obstacle has been the lack of a reproducible method to create specific, optically active defects on demand. Recent advances in ion, neutron, and electron irradiation now offer a pathway to bridge that gap, positioning hBN for integration into photonic circuits and quantum networks.

The new study demonstrates that the formation of negatively charged boron‑vacancy centers (V_B⁻) in suspended CVD‑grown hBN is highly sensitive to the type of bombarding particle. Light ions such as He⁺ and Ne⁺, as well as neutrons, reliably generate V_B⁻ defects that emit at 800 nm, whereas heavier Ar⁺ ions favor alternative centers emitting near 650 nm, identified as anti‑site nitrogen‑vacancy complexes (N_BV_N). Substrate‑supported films introduce secondary particles that alter defect yields, and film thickness further modulates the defect landscape. By coupling photoluminescence spectroscopy with optically detected magnetic resonance (ODMR), the researchers distinguished bright emitters from “dark” paramagnetic defects that affect spin‑lattice relaxation (T₁) and zero‑field splitting, revealing a direct link between defect density and spin dynamics.

These findings unlock a scalable toolbox for quantum photonic manufacturing. Precise control over defect species and spin properties enables deterministic placement of single‑photon sources and spin qubits within wafer‑compatible hBN layers, reducing reliance on labor‑intensive exfoliation. Companies developing quantum communication hardware, integrated photonic chips, and spin‑based sensors can now consider CVD hBN as a viable platform for mass production. Future work will likely focus on optimizing irradiation parameters for uniform defect arrays, integrating hBN with silicon photonics, and exploiting the identified dark defects for quantum memory applications, accelerating the transition from laboratory prototypes to commercial quantum technologies.