Generation and Characterization of Diamond Color Centers Using Ultra-Low-Fluence Ion Implantation at KAERI

Abstract

Diamond color centers provide a versatile solid-state platform capable of operating across multiple defect-density regimes—from ensemble color centers to isolated single emitters—owing to their stable optical emission and controllable spin properties at room temperature. However, the absence of fabrication techniques capable of deterministically controlling this transition has hindered domestic progress toward scalable single-photon–based quantum devices. This study aims to establish an ion- implantation–based fabrication method that enables precise control of defect density and spatial distribution, thereby realizing both ensemble and single diamond color centers within a single integrated platform. Nitrogen and silicon ions were implanted into single-crystal diamond substrates with systematically varied implantation energies and fluences. SRIM simulations were used to estimate the projected ion ranges, which guided the selection of implantation conditions. Through systematic optical and spin characterization of ensemble color centers, optimal annealing temperatures and surface treatment conditions were identified to maximize formation yield and spectral quality. These optimized parameters were subsequently applied to the fabrication of single centers, where we aimed to secure stable single-photon emission despite the inherently low implantation fluences. The optical and spin properties of the fabricated centers were characterized using confocal microscopy, photoluminescence (PL) spectroscopy, and Optically Detected Magnetic Resonance (ODMR). NV centers exhibited resonance splitting at 2.87 GHz, confirming their spin-triplet ground-state characteristics, while SiV centers showed narrow zero-phonon lines suitable for coherent photon emission. Single-photon emission was investigated using a Hanbury–Brown–Twiss interferometer, where the observation of an antibunching dip indicated the potential realization of single-color centers. This work not only demonstrates a reproducible ion-implantation–based process capable of generating both ensemble and single diamond color centers, but also provides a comprehensive optical characterization of the fabricated defects, thereby offering essential insights for future developments in quantum sensing, quantum communication, and photonic devices in Korea.