Enhancement of Coherence Times of Individual Shallow NV Center due to Ozone Treatment

Abstract

Shallow nitrogen vacancy (NV) centers with long coherence times are promising candidates for applications in areas such as quantum computing and quantum sensing. However, as the NVs are only a few nanometers below the diamond's surface, it is a challenge to remove the different decoherence sources related to the surface, e.g., charge fluctuations and magnetic impurities. Here, the effect of ozone treatment on the chemical composition of diamond surfaces was correlated with its impact on the spin properties of the same individual shallow NV (depth < 20 nm) by comparing its coherence times, Ramsey (T2*) and Hahn Echo (T2), before and after the treatment. X-ray photoelectron spectroscopy (XPS) shows a reduction in sp2 bonds, and it was reported that an enhancement of the coherence times up to a factor of 3. Additionally, we investigate the effects of Ozone treatment on random single NVs engineered to have a depth of approx.30 nm, where an enhancement up to a factor of 10 on T2* and up to a factor of 3 on T2 have been observed.