We investigate spin and optical properties of individual nitrogen-vacancy centers located within 1-10 nm from the diamond surface. We observe stable defects with a characteristic optically detected magnetic resonance spectrum down to lowest depth. We also find a small, but systematic spectral broadening for defects shallower than about 2 nm. This broadening is consistent with the presence of a surface paramagnetic impurity layer [Tisler et al., ACS Nano 3, 1959 (2009)] largely decoupled by motional averaging. The observation of stable and well-behaved defects very close to the surface is critical for single-spin sensors and devices requiring nanometer proximity to the target.
@article{arxiv.1201.0871,
title = {Spin Properties of Very Shallow Nitrogen Vacancy Defects in Diamond},
author = {B. K. Ofori-Okai and S. Pezzagna and K. Chang and M. Loretz and R. Schirhagl and Y. Tao and B. A. Moores and K. Groot-Berning and J. Meijer and C. L. Degen},
journal= {arXiv preprint arXiv:1201.0871},
year = {2012}
}