Site-Controlled Carbon Implantation for Quantum Emitter Engineering in Hexagonal Boron Nitride

Position-controlled quantum defects in 2D hexagonal boron nitride (h-BN), providing addressed and controllable quantum states, are important candidates for quantum technologies. Although carbon-doped defect-related single-photon emitters (SPEs) in h-BN have been extensively studied, the fabrication of position-controlled carbon-defect SPEs in h-BN has not yet been achieved. This study presents a novel two-step method involving helium ion (He⁺) focused ion beam (FIB) nanopatterning combined with post-FIB thermal treatment for the highly controlled fabrication of carbon-defect-related SPEs in h-BN. In the first step, He⁺ FIB, utilizing precise control of ion energy and dose, creates localized lattice defects or vacancies at predetermined positions with sub-30 nm spatial resolution. These engineered defects serve as preferential incorporation sites. The second step involves high-temperature annealing in a methane atmosphere. This facilitates selective incorporation of carbon atoms into the predefined defect sites, forming carbon-related defect complexes that act as bright quantum emitters. A secondary annealing step in air is then used to remove surface-deposited amorphous carbon, significantly enhancing the SPE quality. The resulting emitters achieve high brightness up to 6.7 × 10⁶ counts per second and exhibit enhanced single-photon purity (g²(0) < 0.2). It establishes a foundation for the scalable production of precisely positioned SPE arrays in h-BN, paving the way for their seamless integration into advanced silicon-based photonic platforms for quantum information processing, sensing, and communication applications.