Effects of 300 MeV Kr-ion irradiation on defect evolution, photoelectric response, and NV center spin properties in diamond

Studying high-energy heavy-ion irradiation effects on diamond is vital for space deployment of diamond radiation detectors and nitrogen-vacancy (NV) quantum magnetometers. Herein, we perform 300 MeV Kr-ion irradiation and subsequent thermal annealing on HPHT single-crystal diamond. Under the present measurement conditions, no obvious macroscopic graphitization or amorphization is detectable by Raman spectroscopy and X-ray diffraction (XRD), while irradiation-induced defects and deep-level traps impair carrier transport. Molecular dynamics simulations reveal that defects generated by collision cascades account for the performance loss. Thermal annealing markedly boosts NV photoluminescence intensity, which demonstrates the efficient generation of NV centers. Nevertheless, compared with electron-irradiated reference specimens, Kr-ion-irradiated samples exhibit a reduced spin-echo coherence time T₂. An inherent performance trade-off is uncovered in this material system: high NV output can be attained alongside well-maintained crystal lattices, yet residual defects restrain carrier transport and spin coherence performance.