Toward Single-Spin Imaging with Shallow Diamond Nitrogen-Vacancy Centers*

The negatively charged nitrogen-vacancy (NV⁻) center in diamond is emerging as a powerful quantum magnetometer. As an atomic size sensor, an NV⁻ center incorporated into a scanning probe microscope has the potential of imaging molecular structure. To achieve the requisite sensitivity and spatial resolution, it is crucial that NV⁻ centers are located within nanometers from the surface; however, the diamond surface is known to reduce the spin coherence and charge stability of NV⁻ centers, compromising the capacity of single-spin sensitivity. Here, we address charge state instability of single shallow NV⁻ centers both under illumination and in the dark [1]. We identify tunneling to a local electron trap as the mechanism for charge ionization in the dark and develop techniques to control and readout the trap charge state. We demonstrate experimental protocols to mitigate the detrimental effects, and we present progress towards imaging single molecules.

[1] D. Bluvstein, Z. Zhang, and A. C. B. Jayich, arXiv:1810.02058 (2018)