Reduction of surface spin-induced electron spin relaxations in nanodiamonds*

Nanodiamonds (NDs) hosting nitrogen-vacancy (NV) centers are promising for applications of quantum sensing. Long spin relaxation times (T₁ and T₂) are critical for high sensitivity in quantum applications. Our recent study has shown the presence of surface impurities such as dangling bonds and graphite layers [1]. It has also been shown that fluctuations of magnetic fields due to surface spins strongly influence the spin relaxation times in NDs. In this presentation, we discuss the improvement of T₁ and T₂ of single-substitutional nitrogen impurity (P1) centers in NDs by removing the surface spins [2]. By employing high-frequency electron paramagnetic resonance spectroscopy, we verify that the etching of NDs removes surface spins efficiently and significantly reduces their contribution to T₁. We also discuss T₁ and T₂ of NV centers in etched NDs.

References:
[1] Z. Peng et al., J. Chem. Phys. 150, 134702 (2019).
[2] Z. Peng et al., J. Appl. Phys. 128, 054301 (2020).