Epoxy oxidized diamond (111)-(2 × 1) surface for nitrogen-vacancy based quantum sensors

Abstract

Surface functionalization of diamonds is an important topic for the negatively charged nitrogen-vacancy (NV−) center based quantum sensors. We investigate the electronic properties of oxidized diamond (111) surfaces and their effects on the NV− centers using the density of functional theory. The results show that the epoxy oxidized diamond (111) surface has neither surface spin noises nor inter-bandgap states and also has a positive electron affinity (1.85 eV) with nearly 99% preferential alignment of nitrogen-vacancy, indicating the epoxy oxidized (111) surface could be a perfect host of the NV− centers. Additionally, we make further examinations by placing an NV− center ∼1 nm from the epoxy oxidized (111) surface. The results indicate that the epoxy oxidized (111) surface has no obvious effects on the defect levels and optical transitions of the single NV− center. To the best our knowledge, the epoxy oxidized (111)-(2 × 1) surface may be the first diamond surface that not only theoretically satisfies the electronic requirements of shallow NV− centers but can also be fabricated through the oxidization process. Therefore, the epoxy oxidized diamond (111)-(2 × 1) surface is the most promising candidate to be applied in NV-based quantum sensors.