200 keV energy electron irradiation of single-crystal diamond: quantification of vacancy and nitrogen-vacancy production

Physical Review B (2026)
 
Scientists can create useful defects, called color centers, in diamond by exposing it to electrons and then heating it. Some of these defects, such as nitrogen-vacancy (NV) centers, can act as qubits or highly sensitive quantum sensors.

In this study, researchers investigated how deeply these defects form when high-purity diamond is exposed to relatively low-energy electrons. They found that the simplest defects — missing carbon atoms, called vacancies — are most concentrated near the surface and become less common with increasing depth, extending roughly 12 micrometers into the diamond.

The researchers also looked at how the vacancies turn into NV centers when the diamond is heated. Interestingly, the NV centers did not have the same depth distribution as the vacancies. Their results suggest that when there are many more vacancies than nitrogen atoms, some vacancies combine with one another or form other defects instead of becoming NV centers.

This challenges the assumption that the amount of nitrogen in the diamond is always what limits how many NV centers can be created. In other words, simply creating more vacancies does not necessarily produce more NV centers; too many vacancies can actually lead to unwanted defects.

The paper authors, Chloe Newsom, Ben Green, Mark Newton, Lillian Hughes Wyatt and Ania Jayich, conducted this research at the University of California, Santa Barbara and the University of Warwick.