Impact of defect dynamics on the formation of quantum emitters in hexagonal boron nitride

Isolated point defects in hexagonal boron nitride (hBN) are promising candidates for single-photon emitters (SPEs) for quantum technologies. Despite extensive experimental and theoretical studies in recent years, determining unambiguously the microscopic nature of such emitters and how they form in hBN has been challenging. In this work, we combine optical and electron spectroscopy to reveal how nanoscale carbon migration leads to SPEs in hBN. We find that focused electron-beam irradiation of hBN introduces tightly confined carbon clusters at the irradiation epicenter. Subsequent thermal annealing drives the migration of carbon from such an epicenter, leading to the systematic formation of SPEs a few microns away. First-principles calculations reveal that this carbon migration can be described as a combined process of substitutional carbon and boron vacancy hopping across atomic sites. Our findings provide new insights on the formation process of quantum emitters in hBN, opening new possibilities for their creation and control.