Imaging neutron radiation-induced defects in single-crystal chemical vapor deposition diamond at the atomic level

JL Zhang and FT Huang and S Li and GJ Yu and ZF Xu and LF Hei and FX Lv and A Horne and P Wang and M Qi, DIAMOND AND RELATED MATERIALS, 154, 112189 (2025).

DOI: 10.1016/j.diamond.2025.112189

Diamond's exceptional properties make it highly suited for applications in challenging radiation environments. Understanding radiation-induced damage in diamond is crucial for enabling its practical applications and advancing materials science. However, direct imaging of radiation- induced crystal defects at the atomic to nanometer scale remains rare due to diamond's compact lattice structure. Here, we report the atomic- level characterization of crystal defects induced by high-flux fast neutron radiation (up to 3 x 1017n/cm2) in single-crystal chemical vapor deposition diamonds. Through Raman spectroscopy, the phase transition from carbon sp3 to sp2 hybridization was identified, primarily associated with the formation of dumbbell-shaped interstitial defects, which represent the most prominent radiation-induced defects. Using electron energy loss spectroscopy and aberration-corrected transmission electron microscopy, we observed a clustering trend in defect distribution, where sp2-rich clusters manifested as dislocation cluster structures with a density up to 1014 cm-2. Lomer-Cottrell junctions with a Burgers vector of 1/6(110) were identified, offering a possible explanation for defect cluster formation. Radiation-induced point defects were found to be dispersed throughout the diamond lattice, highlighting the widespread nature of primary defect formation. Vacancy defects, along with (111) and (100) oriented dumbbell-shaped interstitial defects induced by high-dose neutron irradiation, were directly imaged, providing microscopic structural evidence that complements spectroscopic studies of point defects. Dynamical simulations combined with an adiabatic recombination-based crystal damage model, provided insights into the correlation between irradiation dose and resulting crystal damage. These findings advance our understanding of neutron-induced radiation damage mechanisms in diamond and contribute to the development of radiation-resistant diamond materials.

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