Controlled Chemical Synthesis of Color Centers in Nanocrystalline Silicon Carbide

Silicon carbide is a promising material for optically and spin-active point defects relevant to quantum applications. Quantum-relevant color centers are commonly generated by irradiation or implantation, which require specialized infrastructure and may introduce collateral lattice damage. Here, we present a chemical approach in which the influence of synthesis temperature, high-energy ball milling, and aluminum addition on formation, polytype distribution, and defect formation in SiC is investigated. We found that it is possible to create quantum-relevant defects throughout the chemical synthesis, and the temperature and mechanical activation are the dominant parameters governing defect generation. Photoluminescence and electron paramagnetic resonance spectroscopy demonstrate that low synthesis temperatures (1050-1150 °C) in high-energy ball-milled samples yield silicon vacancy and divacancy-related color centers, evidenced by characteristic near-infrared PL emission and high-spin EPR signals with zero-field splitting values D ≈ 1.3 GHz and D ≈ 270 MHz, consistent with neutral divacancies and V_Si-C_Si complex centers, respectively. An additional EPR signal at D ≈ 650-780 MHz, not matched by any previously reported defect configuration in SiC, is tentatively assigned to a second-nearest-neighbor divacancy-like (V_Si-V_C) pair.