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

Abstract

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 × 10¹⁷ n/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.