Negatively Charged Nitrogen-Vacancy Centers in a 5 nm Thin 12C Diamond Film

We report successful introduction of negatively charged nitrogen-vacancy (NV-) centers in a 5 nm thin, isotopically enriched ([C-12] 99.99%) diamond layer by CVD. The present method allows for the formation of NV- in such a thin layer even when the surface is terminated by hydrogen atoms. NV- centers are found to have spin coherence times of between T-2 similar to 10-100 mu s at room temperature. Changing the surface termination to oxygen or fluorine leads to a slight increase in the NV- density, but not to any significant change in T2. The minimum detectable Magnetic field estimated by this T-2 is 3 nT after 100 s of averaging, which would be sufficient for the detection of nuclear magnetic fields exerted by a single proton. We demonstrate the suitability for nanoscale NMR by measuring the fluctuating field from similar to 10(4) proton nuclei placed on top of the 5 nm diamond film.