Novel Approach to Promote Nitrogen Aggregation in High-Temperature and High-Pressure Diamonds

Nitrogen impurities remain a hot topic in diamond impurity research, and the mechanism of formation of nitrogen impurities in natural diamonds remains unclear to this day. This study synthesized diamond by doping carbonyl iron powder and CH 4 N 2 S into the FeNiCo-C synthesis system to simulate the multielement synergistic environment of the mantle, aiming to investigate the effects of multiple elements acting together on the existence form and content of nitrogen impurities in diamond. In this study, diamonds synthesized with two dopants contained both A-aggregated nitrogen and C-center nitrogen. Notably, diamonds synthesized by doping CH 4 N 2 S along the (100) crystal plane of the seed crystal exhibited an A-aggregated nitrogen content as high as 63% of the total nitrogen, which is exceptionally rare in unannealed diamonds. Furthermore, we found that under different synthesis systems, nitrogen impurities were more readily incorporated into diamond from the (111) crystal plane. The study revealed that diamonds synthesized by doping CH 4 N 2 S contain NV – defects and none or less than the detection threshold of NV 0 defects. Diamonds synthesized by doping carbonyl iron powder exhibit a higher concentration of NV – defects. The internal stress in diamonds synthesized by doping with CH 4 N 2 S is compressive stress, while that in diamonds synthesized by doping with carbonyl iron powder is tensile stress. This study provides a novel method for synthesizing diamonds with a high proportion of A-aggregated nitrogen, offering an important experimental reference for the formation mechanism of natural diamonds. Simultaneously, it presents a new approach for synthesizing diamonds containing only NV – defects.