The negatively charged nitrogen vacancy (NV−) center in a diamond is a nanometer-sized defect with very sensitive properties that can be manipulated, for example, for single-molecule photoluminescence and nuclear magnetic resonance sensing, as a single photon source for quantum cryptography and as a qubit in room temperature quantum computing. To have a minimal perturbation of its properties, it is important to isolate the NV-center from other defects. One type of the extended defects that can be common in diamonds is the intrinsic stacking fault (ISF) associated with dislocations. In this work, we use density functional theory simulations to investigate how the distance between the NV− center and an ISF affects its properties, including the transition energies, spin density, and energy eigenvalues in the Kohn–Sham bandgap. We have found that the NV-center properties are only slightly perturbed when placed in the vicinity of an ISF. Even for an interdistance of only 3.8 Å between the NV-center and the ISF, the decrease in its zero phonon line (ZPL) energy is less than 6.8%. To more significantly perturb the ZPL, the NV-center has to be placed inside the stacking fault glide plane (11.3% decrease). The changes in ZPL are in the majority of cases lower than the bulk value, which can be used to guide experimental observations. We find that the NV-center is only weakly interacting with ISFs, which in addition to a small bulk conversion depth of 5 Å to a diamond surface is important for their technological use.

The negatively charged nitrogen vacancy centre in diamond is a promising candidate for future nanoscale quantum applications. For its operation it is important to have control of the centres charge state, and to avoid temporary disappearance of the NV-center’s functionality, termed photo-blinking. In this work, we use density functional theory simulations to investigate excitations that result in loss of an electron from NV− to a nearby nitrogen donor (donor-N+), leading to NV0 and donor-N0 charge state, and the corresponding deexcitation. Since these processes involve two different localized defect centres in the diamond lattice (the NV-center and the donor-N) they are non-local excitations. We have studied the de-charging both as a one-photon process and through a sequential two-photon process via the NV-center excited state. We propose de-charging directly from the NV-center to the donor-N as a possible mechanism for photo-blinking of the NV-center that involve an additional electron spin resonance active defect, the donor-N0. We have found that the excitation energies are converged when the distance between the two is larger than 10.4 Å. We also compute excitations to the conduction band edge from NV− (to NV0) and from donor-N0 (to donor-N+) using G0W0 + BSE.

The negatively charged nitrogen vacancy (NV − ) center in diamond has properties that make it a promising candidate for applications such as a qubit in room temperature quantum computing, single-molecule photoluminescence and NMR sensor, and as a single photon source for quantum cryptography. For many of its uses it is desirable to have the NV-center close to the diamond surface. In this work, we use density functional theory simulations to investigate how the distance of the NV − center to a surface, and its orientation, affect its properties, including the zero-phonon-line. We study the three technologically important surfaces terminated with fluorine, oxygen/hydroxyl and nitrogen. Since the NV-center is charged it requires special measures to simulate within a slab-model. We use the recently proposed charging with a substitutional donor in the diamond lattice resulting in a neutral super-cell, which provides very satisfactory results. We have found that the NV-centers properties converge to bulk values already at 5 Å depth.

Charged defects are traditionally computed by adding (subtracting) electrons for negative (positive) impurities. When using periodic boundary conditions this results in artificially charged supercells that also require a compensating background charge of the opposite sign, which makes slab supercells problematic because of an arbitrary dependence on the vacuum thickness. In this work, we test the method of using neutral supercells through the use of a substitutional electron donor (acceptor) to describe charged systems. We use density functional theory (DFT) to compare the effects of charging the well-studied NV-center in diamond by a substitutional donor nitrogen. We investigate the influence of the donor-N on the NV-center properties as a function of the distance between them, and find that they converge toward those obtained when adding an electron. We analyze the spin density and conclude that the donor-N has a zero magnetic moment, and thus, will not be seen in electron spin resonance. We validate our DFT energies through comparison to GW simulations. Charging the NV-center with a substitutional donor-N enables accurate calculations of slabs, without the ambiguity of using charged supercells. Implantation of donor-N atoms opens up the possibility to engineer NVcenters with the desired charge state for future ICT and sensor applications.