Yubin Je received the M.S. degrees in Physics from the Korea Advanced Institute of Science and Technology (KAIST), Republic of Korea. He is currently pursuing the Ph.D. degree through the Hokkaido University–NIMS Joint Graduate School Program.

Optically addressable spin defects in hBN are an attractive platform for probing 2D-material physics because they can be positioned at the surface with a negligible gap to adjacent 2D layers. Carbon-doped hBN is particularly notable for its bright, room-temperature single-color-center emission and high optically detected magnetic resonance contrast.[1, 2] However, conventional carbon doping involves placing hBN crystals in a high-temperature graphite furnace, allowing carbon atoms to diffuse inward from the surface.[3] Because this diffusion creates a carbon concentration gradient between the crystal surface and the center, it is difficult to obtain flakes with uniformly distributed surface-located color centers. Here, we applied additional O₂ plasma and annealing to exfoliated carbon-doped hBN flakes to uniformly generate carbon-oxygen-related color centers at the surface. These color centers exhibit broad emission (580–900 nm) and single-photon behavior at room temperature. For future work, we plan to create spin-addressable color centers over large areas and integrate them with two-dimensional systems, thereby developing a quantum sensing device capable of detecting small physical quantities within the two-dimensional material. As interest in 2D materials continues to grow, quantum sensors using 2D spin defects are expected to play a vital role in investigating 2D systems.

1. A. Chatterjee et al., Science Advances 11, eadv2899 (2025), DOI: 10.1126/sciadv.adv2899
2. C. M. Gilardoni et al., Nature Communications 16, 4947 (2025), DOI: 10.1038/s41467-025-59642-0
3. M. Onodera et al., Carbon 167, 785 (2020), DOI: 10.1016/j.carbon.2020.05.032