This study systematically investigated the optically stimulated luminescence (OSL) characteristics of heteroepitaxial diamond (HED) with two different nitrogen concentrations (3 ppb and 1 ppm). The nitrogen-rich sample exhibited substantially higher OSL intensity than the low-nitrogen sample, reflecting an increased density of trapping sites and luminescent centers associated with nitrogen-related defects. Both samples showed weak dose dependence below 10 Gy and saturation at 100–200 Gy, consistent with the classical center-depletion model. A pronounced enhancement in OSL sensitivity was observed only in the nitrogen-rich sample following pre-irradiation up to 400 Gy. This enhancement is attributed to increased trapped-electron population, activation of previously inactive luminescent centers, and improved radiative recombination efficiency. The enhancement was completely removed by annealing at 500 °C for 60 s, indicating that the effect originates from metastable changes in defect occupancy rather than permanent defect formation. The OSL emission spectra exhibited a single broad band between 500 and 800 nm, peaking at 620–650 nm, corresponding to the phonon sideband of NV⁻-related luminescence. No zero-phonon line at 637 nm was resolved, consistent with the broad-band, phonon-assisted nature of the measured OSL emission. The spectral shape remained unchanged after pre-irradiation. Fading measurements further revealed that the nitrogen-rich diamond possesses more thermally stable trap levels than the low-nitrogen sample. These findings demonstrate that nitrogen incorporation is an effective strategy for tuning the OSL performance of HED and the potential of nitrogen-rich HED for high-dose and reusable dosimetry applications.
Shinsho et al. (Thu,) studied this question.