Structured-Defect Engineering of Hexagonal Boron Nitride for Identified Visible Single-Photon Emitters

Visible-range single-photon emitters (SPEs), based on hexagonal boron nitride (hBN), with exceptional optical performance have become an outstanding candidate for quantum optical technology. However, the control of the carbon defect structures to obtain uniform and confined band structure remains elusive, restricting their integration into on-chip quantum devices. Here, we demonstrate tuning of the defect structure of hBN to precisely control the emission in SPEs. The defect structure engineering from CB (carbon substituted at the boron site) to C₂B-CN (carbon doped into two boron sites and one nitrogen site) carbon defect conversion in hBN is realized by regulating the carbon concentration from 0.0005 at % to 0.082 at % in Cu substrates to adjust the carbon diffusion during the CVD process. Meanwhile, the zero-phonon line exhibits a precise shift from the range of 600-610 nm to 630-640 nm; these shifts of the spectral features are further supported by density functional theory results, reflected in changes in the band structure, vibrational degrees of freedom, and electronic transitions. The SPE emission spectrum serves as a valuable tool for identifying the footprint of a carbon point defect structure change. Our project offers evidence of achieving structured defect engineering for tailored emission properties and showcases potential for the integration of advanced 2D material engineering into on-chip quantum devices.