Visualizing the atomic structure of nitrogen-vacancy color center in diamond by multislice electron ptychography

The structure and distribution of nitrogen-vacancy (NV) centers in diamond are critical for their performance in quantum technologies, such as quantum computing and sensing. For quantum sensing applications, achieving a high density of NV centers is essential, and both the structural arrangement of the ensemble NV centers and their distribution significantly influence sensitivity. However, existing techniques lack the resolution required to accurately characterize the atomic-scale structure, distribution, and strain field of NV centers. In this study, we present the first atomic-scale imaging of ensemble NV center structures using multislice electron ptychography (MEP) in a diamond containing 27 ppm NV centers. Our direct imaging reveals that the ensemble NV centers can be characterized as clusters of individual NV centers, rather than being tightly segregated or randomly distributed at atomic scale. Each NV cluster comprises more than four single NV centers aligned along three or more atomic columns within a depth range of 1-5 nm along [110] projected direction, with the spacing between clusters of approximately 1-2 nm along the (110) projection plane. This work provides valuable insights into the true structural characteristics of dense NV centers, offering guidance for understanding the structure-property correlations that influence their performance in quantum sensing and related applications.