Improvement in Fluorescence Intensity of Color Centers in Diamond by High-Fluence Irradiation

The high transmissivity, high thermal conductivity, and radiation hardness of diamond make it ideal for use in harsh radiative environments. Herein, the influence of 90 keV O+ and H+ as well as 1 MeV electron irradiation with fluence up to 1 × 1017 ions/cm2 on bulk diamond crystals are systematically investigated, in combination with morphological, structural, and optoelectronic characterization. The results show that H+ irradiation increases the electron concentration of diamond, while O+ and electrons show adverse effects. H+ irradiation turns the diamond from colorless to brownish, while O+ irradiation results in a blackness appearance. Although electron irradiation drastically decreases the transmissivity in the near-infrared region (1–2.5 μm) from 33% to only 2%, it still remains visually transparent. Interestingly, irradiation remarkably enhances the room temperature 575, 637, and 738 nm related luminescence, due to the formation of the NV and SiV defects facilitated by irradiation-created vacancies. Compared to H+ and O+ irradiation, electron irradiation creates the strongest defect luminescence (intensified by nearly 9 times) while undergoing moderate radiation damage, which could be employed as an efficient method to tune defect luminescence in diamonds for quantum sensing.