Sulfur in diamond and its effect on the creation of nitrogen-vacancy defect from <i>ab initio</i> simulations

The negatively charged nitrogen-vacancy (NV) center is one of the most significant and widely studied defects in diamond that plays a prominent role in quantum technologies. The precise engineering of the location and concentration of NV centers is of great importance in quantum technology applications. To this end, irradiation techniques such as nitrogen-molecule ion implantation are applied. Recent studies have reported enhanced NV center creation and activation efficiencies introduced by nitrogen molecule ion implantation in doped diamond layers, where the maximum creation efficiency at <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mo>∼</a:mo><a:mn>75</a:mn><a:mo>%</a:mo></a:mrow></a:math> has been achieved in sulfur-doped layers. However, the microscopic mechanisms behind these observations and the limits of the efficiencies are far from understood. In this study, we employ hybrid density-functional-theory calculations to compute the formation energies, charge transition levels, and the magneto-optical properties of various sulfur defects in diamond where we also consider the interaction of sulfur and hydrogen in chemical vapor-deposited diamond layers. Our results imply that the competition between the donor substitutional sulfur and the hyperdeep acceptor sulfur-vacancy complex is an important limiting factor on the creation efficiency of the NV center in diamond. However, both species are able to trap interstitial hydrogen from diamond, which favorably mediates the creation of NV centers in chemical vapor-deposited diamond layers.