Efficient generation of nitrogen vacancy centers by laser writing close to the diamond surface with a layer of silicon nanoballs

Abstract

We proposed a method to effectively fabricate negatively charged nitrogen vacancy (NV − ) centers close to the diamond surface by applying femtosecond laser writing technique. With a thick layer of silicon (Si) nanoballs coated, diamond surface was irradiated by high-fluence femtosecond laser pulses. A large number of NV − centers were created around the laser ablation crater area without thermal annealing. The distribution of the NV − centers was expanded to about 50 μm away from the crater center. To demonstrate the function of Si nanoballs, we performed the exactly same laser illumination process on the bare region of the sample surface. In this case, only a few NV − centers were generated around ablation crater. At distance of 32 μm away from crater centers, the NV − density for the case with nanoballs was up to 15.5 times higher compared to the case without nanoballs. Furthermore, we also investigated the influence of laser fluence and pulse number on the NV − density for the case with Si-nanoball layer. Finally, the formation mechanism of NV − centers and the role of Si nanoballs were explained via Coulomb explosion model. The method is demonstrated to be a promising approach to efficiently and rapidly fabricate NV − centers close to the surface of the diamond, which are significant in quantum sensing. Furthermore, the results provide deep insights into complex light-matter interactions.

Preparations and applications of single color centers in diamond

“…Compared to the methods above, this method is convenient and time-saving to generate SiV centers in diamond. In addition to SiV color centers, it's interesting that a large number of NV color centers can be observed in the area irradiated by fs laser even before annealing in our experiment [86]. This indicates that a layer of Si nanoball coated on the diamond surface has the effect of annealing in the forming process of NV color centers.…”

“…These high-energy electrons can blast the crystal lattice of diamond to generate a large number of lattice vacancies, but the conventional annealing process is still required to make these vacancies move to form the NV color centers. And a large number of NV color centers can be directly produced in a diamond-coated with silicon nano-ball in the area of the plasma channel created by femtosecond laser without annealing [86]. Here, it is worth noting that coulomb explosion effect caused by the femtosecond laser interaction with silicon nano-ball not only can implant a doped silicon ions into diamond lattice, but also contributes to the diffusion of the vacancies.…”

Laser Writing of Color Centers

“…Their follow-up work demonstrated that more vacancies were generated in regions of nanoballs and that nitrogen atoms in the air were ionized and doped into the diamond. [122] Therefore, NV centers were also more efficiently created near the diamond surface with the help of Si nanoballs, as shown in Figure 6d. In principle, the method works for other group IV defects in diamond and other materials.…”

“…For some photonic applications that depend on defects close to the surface, such as quantum sensing, the "surface color center" is required to achieve high sensitivity. The reason is that the distance between the spin defects and the sample plays a vital role [122] Copyright 2020, Institute of Physics. (a,b) Reproduced with permission.…”

“…d) The NV center density at different distances from the exposed center with Si nanoball and without Si nanoball. Reproduced with permission [122]. Copyright 2020, Institute of Physics.…”