Defect Engineering in Hexagonal Boron Nitride: Optical Properties of Stable Defect Complexes Arising from Boron Interstitials

Hexagonal boron nitride (hBN) has emerged as a promising candidate material for solid-state quantum technologies due to its wide-band-gap and the potential for defect engineering. Ion- or electron-irradiation is a popular approach to intentionally create boron vacancies in hBN, and there has been significant focus on the optical properties of boron vacancies as potential quantum emitters. In this work [1], we show that the boron ions/atoms ejected from the lattice upon irradiation can be stabilised at existing impurity sites, such as carbon substitutional impurities. The resulting complexes are predicted to be stable at room temperature, and our first principles calculations, including excitonic effects, show that the defects have low-energy optical transitions that are isolated in energy, thus making them suitable as quantum emitters. Our results shed light on recent ion-irradiation experiments [2] on hBN, where single photon emission is observed to occur from sites that are microns away from the irradiated area; this emission is likely to arise from boron ions/atoms that diffuse away from the irradiated area and subsequently combine with existing defects to form defect complexes. This study provides fresh insights into the field of quantum emitters in hBN.

References:

[1] Cheng, N. L. Q.; Ulman, K. A.; Quek, S.Y., Defect Engineering in Hexagonal Boron Nitride: Optical Properties of Stable Defect Complexes Arising from Boron Interstitials, ACS Applied Materials and Interfaces, 2025, 17, 16, 24058-24070

[2] Liang, H.; Chen, Y.; Loh, L.; Cheng, N. L. Q.; Chen, Y.; Yang, C.; Zhang, Z.; Watanabe, K.; Taniguchi, T.; Quek, S. Y.; Bosman, M.; Eda, G.; Bettiol, A. Site-Selective Creation of Blue Emitters in Hexagonal Boron Nitride, ACS Nano, 2025, 19, 15, 15130–15138